Phosphoinositide Binding Regulates α-Actinin Dynamics

The active association-dissociation of dynamic protein-protein interactions is critical for the ability of the actin cytoskeleton to remodel. To determine the influence of phosphoinositide binding on the dynamic interaction of α-actinin with actin filaments and integrin adhesion receptors, fluorescence recovery after photobleaching (FRAP) microscopy was carried out comparing wild-type green fluorescent protein (GFP)-α-actinin and a GFP-α-actinin mutant with a decreased affinity for phosphoinositides (Fraley, T. S., Tran, T. C., Corgan, A. M., Nash, C. A., Hao, J., Critchley, D. R., and Greenwood, J. A. (2003) J. Biol. Chem. 278, 24039–24045). In fibroblasts, recovery of the mutant α-actinin protein was 2.2 times slower than the wild type along actin stress fibers and 1.5 times slower within focal adhesions. FRAP was also measured in U87MG glioblastoma cells, which have higher levels of 3-phosphorylated phosphoinositides. As expected, α-actinin turnover for both the stress fiber and focal adhesion populations was faster in U87MG cells compared with fibroblasts with recovery of the mutant protein slower than the wild type along actin stress fibers. To understand the influence of α-actinin turnover on the modulation of the actin cytoskeleton, wild-type or mutant α-actinin was co-expressed with constitutively active phosphoinositide (PI) 3-kinase. Co-expression with the α-actinin mutant inhibited actin reorganization with the appearance of enlarged α-actinin containing focal adhesions. These results demonstrate that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors and that the dynamics of α-actinin is important for PI 3-kinase-induced reorganization of the actin cytoskeleton. In conclusion, phosphoinositide regulation of α-actinin dynamics modulates the plasticity of the actin cytoskeleton influencing remodeling. The active association-dissociation of dynamic protein-protein interactions is critical for the ability of the actin cytoskeleton to remodel. To determine the influence of phosphoinositide binding on the dynamic interaction of α-actinin with actin filaments and integrin adhesion receptors, fluorescence recovery after photobleaching (FRAP) microscopy was carried out comparing wild-type green fluorescent protein (GFP)-α-actinin and a GFP-α-actinin mutant with a decreased affinity for phosphoinositides (Fraley, T. S., Tran, T. C., Corgan, A. M., Nash, C. A., Hao, J., Critchley, D. R., and Greenwood, J. A. (2003) J. Biol. Chem. 278, 24039–24045). In fibroblasts, recovery of the mutant α-actinin protein was 2.2 times slower than the wild type along actin stress fibers and 1.5 times slower within focal adhesions. FRAP was also measured in U87MG glioblastoma cells, which have higher levels of 3-phosphorylated phosphoinositides. As expected, α-actinin turnover for both the stress fiber and focal adhesion populations was faster in U87MG cells compared with fibroblasts with recovery of the mutant protein slower than the wild type along actin stress fibers. To understand the influence of α-actinin turnover on the modulation of the actin cytoskeleton, wild-type or mutant α-actinin was co-expressed with constitutively active phosphoinositide (PI) 3-kinase. Co-expression with the α-actinin mutant inhibited actin reorganization with the appearance of enlarged α-actinin containing focal adhesions. These results demonstrate that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors and that the dynamics of α-actinin is important for PI 3-kinase-induced reorganization of the actin cytoskeleton. In conclusion, phosphoinositide regulation of α-actinin dynamics modulates the plasticity of the actin cytoskeleton influencing remodeling. The dynamic nature of the actin cytoskeleton is essential for various aspects of intracellular physiology and function as well as the ability of the cell to respond to signals stimulating cellular processes such as proliferation, differentiation, and migration. Individual protein molecules exchange between structures and the cytoplasm and/or membrane keeping the actin cytoskeleton pliable and able to quickly respond to signals inducing reorganization. In this report, we will refer to this dynamic exchange of proteins as turnover. Much of what we know about actin dynamics on the regulation of actin proteins the of cells T. Biol. is actin proteins influence actin dynamics and in the These proteins have to active in the modulation of actin have in the as of actin cytoskeleton the proteins actin In this we on the influence of actin on the of the actin actin protein that a between actin stress fibers and integrin receptors within focal α-actinin is a protein for the of the actin cytoskeleton C. Biol. The of α-actinin along actin stress fibers interaction of the actin binding of the with actin J. Biol. A. D. J. A. C. A. J. is to focal as a of interactions with actin filaments within the stress fiber and integrin adhesion receptors A. J. Biol. Chem. Biol. recovery after photobleaching (FRAP) fluorescence recovery after green fluorescent of PI phosphoinositide fluorescence recovery after green fluorescent of PI phosphoinositide microscopy of α-actinin along stress fibers the association-dissociation rate of α-actinin with actin filaments within FRAP of α-actinin within focal is a of the association-dissociation rate of α-actinin with actin filaments and the dynamics of α-actinin in cells GFP-α-actinin FRAP C. Biol. D. C. J. is what the rate of α-actinin turnover. proteins interactions with phosphoinositides and and we have that α-actinin is phosphoinositide binding J. Biol. J. J. Biol. Chem. C. J. we have that the binding of and the of α-actinin and that binding α-actinin J. J. Biol. Chem. C. J. and interaction with the of integrin adhesion receptors J. Biol. of within the phosphoinositide binding of α-actinin decreased binding to phosphoinositides as as J. J. Biol. Chem. the mutant protein to have in actin filaments the of the actin cytoskeleton J. J. Biol. Chem. results that phosphoinositide regulation of α-actinin was the of the actin cytoskeleton, the which phosphoinositides α-actinin in the cell was In this we the GFP-α-actinin wild-type and mutant proteins to the regulation of α-actinin turnover phosphoinositide The results that phosphoinositide binding regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors influencing the plasticity of the actin cytoskeleton and ability to carried out with D. C. J. Biol. fibroblasts and U87MG glioblastoma cells in on and with wild-type and mutant as J. J. Biol. Chem. after cells to the with of a and for fluorescence was with a with the of a and a dynamic the the of with or photobleaching the recovery cells GFP-α-actinin of and for the FRAP To to the cells the of was for stress fibers and for focal was to photobleaching to the fluorescence and with the to the of to of the for for the and for the of the stress fibers on the cytoskeleton or of the photobleaching of focal on of the was for cells, the both wild-type and mutant and was recovery the of recovery was the to of the To the of in fluorescence was the recovery with as the for the after the and U87MG the compared between cell after of the to of in the as The for mutant cells to have than wild-type cells to the of the and for and U87MG the was a of on a and the after for both of with for The was as D. C. J. with wild type or mutant and as a the J. J. after cells with in for cells with with in with in and with to PI cells and to of the cells a with a determine the influence of phosphoinositide binding on the association-dissociation rate of α-actinin with actin FRAP microscopy was carried out comparing wild-type GFP-α-actinin and the GFP-α-actinin mutant with a decreased affinity for phosphoinositides J. J. Biol. Chem. proteins in as J. J. Biol. Chem. of containing α-actinin stress fibers within cells was and fluorescence recovery within the a recovery of GFP-α-actinin along the stress fibers with a of and of the fluorescence and These within the of for GFP-α-actinin cellular and C. Biol. D. C. J. J. of the GFP-α-actinin mutant was 2.2 times slower than the wild-type protein with a of and than of the fluorescence and carried out on comparing cells the wild-type or mutant the was slower for the GFP-α-actinin mutant compared with the wild-type protein The for wild-type and mutant α-actinin that phosphoinositide binding regulates the rate of turnover and the ability of the protein to of FRAP the turnover of α-actinin along actin stress recovery for GFP-α-actinin wild type and mutant the of wild-type and mutant GFP-α-actinin is for cell the GFP-α-actinin mutant a slower rate compared with the wild of the for the wild-type cells on with of the of cells of between the wild-type and mutant stress fibers or focal and U87MG glioblastoma in a These results that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with the actin filaments within stress fibers. important is the of α-actinin the actin filaments in stress fibers is to and with phosphoinositides. In to the results and the GFP-α-actinin mutant J. J. Biol. Chem. and A. J. Biol. Chem. that α-actinin with the along actin stress fibers. T. T. J. Biol. Chem. of and α-actinin along actin stress fibers. These results that this of α-actinin is in to membrane the association-dissociation rate of α-actinin with actin filaments and integrin receptors within focal adhesions. FRAP of GFP-α-actinin within focal carried out as for the stress fiber on the cells in the The and of the focal in the both the wild-type and mutant proteins cell to As J. J. Biol. Chem. have in the focal of wild-type α-actinin compared with the mutant of α-actinin within focal was times faster than stress fibers was as The turnover of α-actinin within focal was 1.5 times slower for the mutant protein compared with the wild-type These results that phosphoinositide binding regulates the association-dissociation rate of α-actinin with actin filaments and integrin receptors within focal a influence was on the association-dissociation rate of α-actinin with actin filaments within stress fibers. is the rate of turnover for the α-actinin within focal is faster compared with stress The rate of turnover the of phosphoinositides and PI which have to to focal J. Biol. The focal adhesion of α-actinin also to in to the membrane the for interaction with phosphoinositides. In the affinity of α-actinin is higher for actin filaments than integrin receptors J. Biol. binding regulates the association-dissociation rate of α-actinin with actin filaments and within focal adhesions. GFP-α-actinin wild type or mutant with fluorescence and for the FRAP of containing a focal adhesion was for FRAP carried out as and of the cell to photobleaching is with the of of the of photobleaching and after and of recovery also the of phosphoinositides in α-actinin turnover was measured in U87MG glioblastoma cells, which the J. C. D. J. C. and have higher levels of the 3-phosphorylated phosphoinositides compared with cells the A. As expected, α-actinin turnover for both the stress fiber and focal adhesion populations was faster in U87MG cells compared with with recovery of the wild-type protein faster than the mutant along actin stress fibers These results the that phosphoinositide binding regulates the turnover of α-actinin in the wild-type and mutant proteins the rate within the focal of U87MG is a rate was between the wild-type and mutant proteins in the focal of determine the influence of α-actinin turnover on the of the actin cytoskeleton, to wild-type or mutant GFP-α-actinin with constitutively active PI 3-kinase. A. D. A. J. that of constitutively active PI in fibroblasts in levels of which was the of with The of 3-phosphorylated phosphoinositides PI the actin cytoskeleton to and membrane A. D. A. J. reorganization in the wild-type cells was with A. D. A. J. in membrane and a of stress fibers and focal As expected, α-actinin with In PI to membrane as well as the with the on the actin cytoskeleton or of the cells of the mutant protein with constitutively active PI was to actin reorganization with the appearance of enlarged α-actinin containing focal for PI was within the focal of of cells as well as in the membrane and These results that the rate of α-actinin as phosphoinositide the ability of the actin cytoskeleton to remodel. we that of the α-actinin mutant actin reorganization and the of focal the in the of α-actinin containing focal was PI to important in and of integrin receptors in the of the α-actinin which was the of the focal have in the of focal adhesion α-actinin turnover is for PI 3-kinase-induced of the actin cytoskeleton. with wild type or mutant and and for fluorescence microscopy as and of GFP-α-actinin actin and constitutively active PI the cell the wild-type or mutant protein of results in this to in a J. Biol. we binding to α-actinin in cells, and of with binding with the reorganization of the actin cytoskeleton and of membrane was to α-actinin of with with the of actin stress fibers and of the focal adhesions. that and α-actinin within the the regulates α-actinin rate of turnover and interaction with actin The regulation of α-actinin turnover as a influencing the plasticity of the actin cytoskeleton. which is in to the of the active and of the α-actinin between the integrin adhesion receptors and actin filaments in the of focal and of stress we have α-actinin mutant with a decreased affinity for phosphoinositides to demonstrate that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors in α-actinin turnover the plasticity and of the actin cytoskeleton. As as we this is the to that phosphoinositide binding protein-protein interaction dynamics in the cell and the regulation of protein turnover as a for the of the actin cytoskeleton. The dynamic nature of the actin cytoskeleton is essential for various aspects of intracellular physiology and function as well as the ability of the cell to respond to signals stimulating cellular processes such as proliferation, differentiation, and migration. Individual protein molecules exchange between structures and the cytoplasm and/or membrane keeping the actin cytoskeleton pliable and able to quickly respond to signals inducing reorganization. In this report, we will refer to this dynamic exchange of proteins as turnover. Much of what we know about actin dynamics on the regulation of actin proteins the of cells T. Biol. is actin proteins influence actin dynamics and in the These proteins have to active in the modulation of actin have in the as of actin cytoskeleton the proteins actin In this we on the influence of actin on the of the actin cytoskeleton. As actin protein that a between actin stress fibers and integrin receptors within focal α-actinin is a protein for the of the actin cytoskeleton C. Biol. The of α-actinin along actin stress fibers interaction of the actin binding of the with actin J. Biol. A. D. J. A. C. A. J. is to focal as a of interactions with actin filaments within the stress fiber and integrin adhesion receptors A. J. Biol. Chem. Biol. recovery after photobleaching (FRAP) fluorescence recovery after green fluorescent of PI phosphoinositide fluorescence recovery after green fluorescent of PI phosphoinositide microscopy of α-actinin along stress fibers the association-dissociation rate of α-actinin with actin filaments within FRAP of α-actinin within focal is a of the association-dissociation rate of α-actinin with actin filaments and the dynamics of α-actinin in cells GFP-α-actinin FRAP C. Biol. D. C. J. is what the rate of α-actinin turnover. proteins interactions with phosphoinositides and and we have that α-actinin is phosphoinositide binding J. Biol. J. J. Biol. Chem. C. J. we have that the binding of and the of α-actinin and that binding α-actinin J. J. Biol. Chem. C. J. and interaction with the of integrin adhesion receptors J. Biol. of within the phosphoinositide binding of α-actinin decreased binding to phosphoinositides as as J. J. Biol. Chem. the mutant protein to have in actin filaments the of the actin cytoskeleton J. J. Biol. Chem. results that phosphoinositide regulation of α-actinin was the of the actin cytoskeleton, the which phosphoinositides α-actinin in the cell was In this we the GFP-α-actinin wild-type and mutant proteins to the regulation of α-actinin turnover phosphoinositide The results that phosphoinositide binding regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors influencing the plasticity of the actin cytoskeleton and ability to remodel. carried out with D. C. J. Biol. fibroblasts and U87MG glioblastoma cells in on and with wild-type and mutant as J. J. Biol. Chem. after cells to the with of a and for fluorescence was with a with the of a and a dynamic the the of with or photobleaching the recovery cells GFP-α-actinin of and for the FRAP To to the cells the of was for stress fibers and for focal was to photobleaching to the fluorescence and with the to the of to of the for for the and for the of the stress fibers on the cytoskeleton or of the photobleaching of focal on of the was for cells, the both wild-type and mutant and was recovery the of recovery was the to of the To the of in fluorescence was the recovery with as the for the after the and U87MG the compared between cell after of the to of in the as The for mutant cells to have than wild-type cells to the of the and for and U87MG the was a of on a and the after for both of with for The was as D. C. J. with wild type or mutant and as a the J. J. after cells with in for cells with with in with in and with to PI cells and to of the cells a with a FRAP carried out with D. C. J. Biol. fibroblasts and U87MG glioblastoma cells in on and with wild-type and mutant as J. J. Biol. Chem. after cells to the with of a and for fluorescence was with a with the of a and a dynamic the the of with or photobleaching the recovery cells GFP-α-actinin of and for the FRAP To to the cells the of was for stress fibers and for focal was to photobleaching to the fluorescence and with the to the of to of the for for the and for the of the stress fibers on the cytoskeleton or of the photobleaching of focal on of the was for cells, the both wild-type and mutant and was recovery the of recovery was the to of the To the of in fluorescence was the recovery with as the for the after the and U87MG the compared between cell after of the to of in the as The for mutant cells to have than wild-type cells to the of the and for and U87MG the was a of on a and the after for both of with for The was as D. C. J. with wild type or mutant and as a the J. J. after cells with in for cells with with in with in and with to PI cells and to of the cells a with a determine the influence of phosphoinositide binding on the association-dissociation rate of α-actinin with actin FRAP microscopy was carried out comparing wild-type GFP-α-actinin and the GFP-α-actinin mutant with a decreased affinity for phosphoinositides J. J. Biol. Chem. proteins in as J. J. Biol. Chem. of containing α-actinin stress fibers within cells was and fluorescence recovery within the a recovery of GFP-α-actinin along the stress fibers with a of and of the fluorescence and These within the of for GFP-α-actinin cellular and C. Biol. D. C. J. J. of the GFP-α-actinin mutant was 2.2 times slower than the wild-type protein with a of and than of the fluorescence and carried out on comparing cells the wild-type or mutant the was slower for the GFP-α-actinin mutant compared with the wild-type protein The for wild-type and mutant α-actinin that phosphoinositide binding regulates the rate of turnover and the ability of the protein to with of the of cells of between the wild-type and mutant stress fibers or focal and U87MG glioblastoma in a These results that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with the actin filaments within stress fibers. important is the of α-actinin the actin filaments in stress fibers is to and with phosphoinositides. In to the results and the GFP-α-actinin mutant J. J. Biol. Chem. and A. J. Biol. Chem. that α-actinin with the along actin stress fibers. T. T. J. Biol. Chem. of and α-actinin along actin stress fibers. These results that this of α-actinin is in to membrane the association-dissociation rate of α-actinin with actin filaments and integrin receptors within focal adhesions. FRAP of GFP-α-actinin within focal carried out as for the stress fiber on the cells in the The and of the focal in the both the wild-type and mutant proteins cell to As J. J. Biol. Chem. have in the focal of wild-type α-actinin compared with the mutant of α-actinin within focal was times faster than stress fibers was as The turnover of α-actinin within focal was 1.5 times slower for the mutant protein compared with the wild-type These results that phosphoinositide binding regulates the association-dissociation rate of α-actinin with actin filaments and integrin receptors within focal a influence was on the association-dissociation rate of α-actinin with actin filaments within stress fibers. is the rate of turnover for the α-actinin within focal is faster compared with stress The rate of turnover the of phosphoinositides and PI which have to to focal J. Biol. The focal adhesion of α-actinin also to in to the membrane the for interaction with phosphoinositides. In the affinity of α-actinin is higher for actin filaments than integrin receptors J. Biol. binding regulates the association-dissociation rate of α-actinin with actin filaments and within focal adhesions. GFP-α-actinin wild type or mutant with fluorescence and for the FRAP of containing a focal adhesion was for FRAP carried out as and of the cell to photobleaching is with the of of the of photobleaching and after and of recovery also the of phosphoinositides in α-actinin turnover was measured in U87MG glioblastoma cells, which the J. C. D. J. C. and have higher levels of the 3-phosphorylated phosphoinositides compared with cells the A. As expected, α-actinin turnover for both the stress fiber and focal adhesion populations was faster in U87MG cells compared with with recovery of the wild-type protein faster than the mutant along actin stress fibers These results the that phosphoinositide binding regulates the turnover of α-actinin in the wild-type and mutant proteins the rate within the focal of U87MG is a rate was between the wild-type and mutant proteins in the focal of determine the influence of α-actinin turnover on the of the actin cytoskeleton, to wild-type or mutant GFP-α-actinin with constitutively active PI 3-kinase. A. D. A. J. that of constitutively active PI in fibroblasts in levels of which was the of with The of 3-phosphorylated phosphoinositides PI the actin cytoskeleton to and membrane A. D. A. J. reorganization in the wild-type cells was with A. D. A. J. in membrane and a of stress fibers and focal As expected, α-actinin with In PI to membrane as well as the with the on the actin cytoskeleton or of the cells of the mutant protein with constitutively active PI was to actin reorganization with the appearance of enlarged α-actinin containing focal for PI was within the focal of of cells as well as in the membrane and These results that the rate of α-actinin as phosphoinositide the ability of the actin cytoskeleton to remodel. we that of the α-actinin mutant actin reorganization and the of focal the in the of α-actinin containing focal was PI to important in and of integrin receptors in the of the α-actinin which was the of the focal have in the of focal adhesion α-actinin turnover is for PI 3-kinase-induced of the actin cytoskeleton. with wild type or mutant and and for fluorescence microscopy as and of GFP-α-actinin actin and constitutively active PI the cell the wild-type or mutant protein of results in this to in a J. Biol. we binding to α-actinin in cells, and of with binding with the reorganization of the actin cytoskeleton and of membrane was to α-actinin of with with the of actin stress fibers and of the focal adhesions. that and α-actinin within the the regulates α-actinin rate of turnover and interaction with actin The regulation of α-actinin turnover as a influencing the plasticity of the actin cytoskeleton. which is in to the of the active and of the α-actinin between the integrin adhesion receptors and actin filaments in the of focal and of stress we have α-actinin mutant with a decreased affinity for phosphoinositides to demonstrate that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors in α-actinin turnover the plasticity and of the actin cytoskeleton. As as we this is the to that phosphoinositide binding protein-protein interaction dynamics in the cell and the regulation of protein turnover as a for the of the actin cytoskeleton. To determine the influence of phosphoinositide binding on the association-dissociation rate of α-actinin with actin FRAP microscopy was carried out comparing wild-type GFP-α-actinin and the GFP-α-actinin mutant with a decreased affinity for phosphoinositides J. J. Biol. Chem. proteins in as J. J. Biol. Chem. of containing α-actinin stress fibers within cells was and fluorescence recovery within the a recovery of GFP-α-actinin along the stress fibers with a of and of the fluorescence and These within the of for GFP-α-actinin cellular and C. Biol. D. C. J. J. of the GFP-α-actinin mutant was 2.2 times slower than the wild-type protein with a of and than of the fluorescence and carried out on comparing cells the wild-type or mutant the was slower for the GFP-α-actinin mutant compared with the wild-type protein The for wild-type and mutant α-actinin that phosphoinositide binding regulates the rate of turnover and the ability of the protein to These results that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with the actin filaments within stress fibers. important is the of α-actinin the actin filaments in stress fibers is to and with phosphoinositides. In to the results and the GFP-α-actinin mutant J. J. Biol. Chem. and A. J. Biol. Chem. that α-actinin with the along actin stress fibers. T. T. J. Biol. Chem. of and α-actinin along actin stress fibers. These results that this of α-actinin is in to membrane phosphoinositides. the association-dissociation rate of α-actinin with actin filaments and integrin receptors within focal adhesions. FRAP of GFP-α-actinin within focal carried out as for the stress fiber on the cells in the The and of the focal in the both the wild-type and mutant proteins cell to As J. J. Biol. Chem. have in the focal of wild-type α-actinin compared with the mutant of α-actinin within focal was times faster than stress fibers was as The turnover of α-actinin within focal was 1.5 times slower for the mutant protein compared with the wild-type These results that phosphoinositide binding regulates the association-dissociation rate of α-actinin with actin filaments and integrin receptors within focal a influence was on the association-dissociation rate of α-actinin with actin filaments within stress fibers. is the rate of turnover for the α-actinin within focal is faster compared with stress The rate of turnover the of phosphoinositides and PI which have to to focal J. Biol. The focal adhesion of α-actinin also to in to the membrane the for interaction with phosphoinositides. In the affinity of α-actinin is higher for actin filaments than integrin receptors J. Biol. To the of phosphoinositides in α-actinin turnover was measured in U87MG glioblastoma cells, which the J. C. D. J. C. and have higher levels of the 3-phosphorylated phosphoinositides compared with cells the A. As expected, α-actinin turnover for both the stress fiber and focal adhesion populations was faster in U87MG cells compared with with recovery of the wild-type protein faster than the mutant along actin stress fibers These results the that phosphoinositide binding regulates the turnover of α-actinin in the wild-type and mutant proteins the rate within the focal of U87MG is a rate was between the wild-type and mutant proteins in the focal of To determine the influence of α-actinin turnover on the of the actin cytoskeleton, to wild-type or mutant GFP-α-actinin with constitutively active PI 3-kinase. A. D. A. J. that of constitutively active PI in fibroblasts in levels of which was the of with The of 3-phosphorylated phosphoinositides PI the actin cytoskeleton to and membrane A. D. A. J. reorganization in the wild-type cells was with A. D. A. J. in membrane and a of stress fibers and focal As expected, α-actinin with In PI to membrane as well as the with the on the actin cytoskeleton or of the cells of the mutant protein with constitutively active PI was to actin reorganization with the appearance of enlarged α-actinin containing focal for PI was within the focal of of cells as well as in the membrane and These results that the rate of α-actinin as phosphoinositide the ability of the actin cytoskeleton to remodel. we that of the α-actinin mutant actin reorganization and the of focal the in the of α-actinin containing focal was PI to important in and of integrin receptors in the of the α-actinin which was the of the focal have in the of focal adhesion The results in this to in a J. Biol. we binding to α-actinin in cells, and of with binding with the reorganization of the actin cytoskeleton and of membrane was to α-actinin of with with the of actin stress fibers and of the focal adhesions. that and α-actinin within the the regulates α-actinin rate of turnover and interaction with actin The regulation of α-actinin turnover as a influencing the plasticity of the actin cytoskeleton. which is in to the of the active and of the α-actinin between the integrin adhesion receptors and actin filaments in the of focal and of stress fibers. In we have α-actinin mutant with a decreased affinity for phosphoinositides to demonstrate that the binding of phosphoinositides regulates the association-dissociation rate of α-actinin with actin filaments and integrin adhesion receptors in α-actinin turnover the plasticity and of the actin cytoskeleton. As as we this is the to that phosphoinositide binding protein-protein interaction dynamics in the cell and the regulation of protein turnover as a for the of the actin cytoskeleton. for critical of the and for the was in the of and and of the of of to for with the