Shank2 Associates with and Regulates Na+/H+ Exchanger 3

Na+/H+ exchanger 3 (NHE3) plays a pivotal role in transepithelial Na+ and HCO3- absorption across a wide range of epithelia in the digestive and renal-genitourinary systems. Accumulating evidence suggests that PDZ-based adaptor proteins play an important role in regulating the trafficking and activity of NHE3. A search for NHE3-binding modular proteins using yeast two-hybrid assays led us to the PDZ-based adaptor Shank2. The interaction between Shank2 and NHE3 was further confirmed by immunoprecipitation and surface plasmon resonance studies. When expressed in PS120/NHE3 cells, Shank2 increased the membrane expression and basal activity of NHE3 and attenuated the cAMP-dependent inhibition of NHE3 activity. Furthermore, knock-down of native Shank2 expression in Caco-2 epithelial cells by RNA interference decreased NHE3 protein expression as well as activity but amplified the inhibitory effect of cAMP on NHE3. These results indicate that Shank2 is a novel NHE3 interacting protein that is involved in the fine regulation of transepithelial salt and water transport through affecting NHE3 expression and activity. Na+/H+ exchanger 3 (NHE3) plays a pivotal role in transepithelial Na+ and HCO3- absorption across a wide range of epithelia in the digestive and renal-genitourinary systems. Accumulating evidence suggests that PDZ-based adaptor proteins play an important role in regulating the trafficking and activity of NHE3. A search for NHE3-binding modular proteins using yeast two-hybrid assays led us to the PDZ-based adaptor Shank2. The interaction between Shank2 and NHE3 was further confirmed by immunoprecipitation and surface plasmon resonance studies. When expressed in PS120/NHE3 cells, Shank2 increased the membrane expression and basal activity of NHE3 and attenuated the cAMP-dependent inhibition of NHE3 activity. Furthermore, knock-down of native Shank2 expression in Caco-2 epithelial cells by RNA interference decreased NHE3 protein expression as well as activity but amplified the inhibitory effect of cAMP on NHE3. These results indicate that Shank2 is a novel NHE3 interacting protein that is involved in the fine regulation of transepithelial salt and water transport through affecting NHE3 expression and activity. Maintenance of intracellular and systemic pH, Na+ concentration, and fluid volume is essential for maintaining the physiological status in cells and whole organisms (1Wakabayashi S. Shigekawa M. Pouyssegur J. Physiol. Rev. 1997; 77: 51-74Crossref PubMed Scopus (563) Google Scholar, 2Zachos N.C. Tse M. Donowitz M. Annu. Rev. Physiol. 2005; 67: 411-443Crossref PubMed Scopus (305) Google Scholar). First demonstrated almost 30 years ago (3Murer H. Hopfer U. Kinne R. Biochem. J. 1976; 154: 597-602Crossref PubMed Scopus (419) Google Scholar), members of the mammalian Na+/H+ exchanger (NHE) 2The abbreviations used are: NHENa+/H+ exchangerPKAcAMP-dependent protein kinasePKA-anchoring proteincAMP-dependent protein kinase anchoring proteinEIPA5-(N-ethyl-N-isopropyl) amiloridePDZPSD-95/discs large/ZO-1PCDpost-confluent dayPSDpost-synaptic densitysiRNAsmall interfering RNACMVcytomegalovirusaaamino acid(s)ESTexpress sequence tagKCLBKorea Cell Line Bank. family participate in the regulation of these parameters at both cellular and systemic levels. To date, nine NHE family members have been identified in mammalian cells with unique tissue distribution and functional properties (2Zachos N.C. Tse M. Donowitz M. Annu. Rev. Physiol. 2005; 67: 411-443Crossref PubMed Scopus (305) Google Scholar). As a better characterized isoform, NHE3 is primarily found in the apical membrane of epithelial cells of the renal and gastrointestinal tracts, where it mediates transepithelial absorption of Na+ and HCO3- (2Zachos N.C. Tse M. Donowitz M. Annu. Rev. Physiol. 2005; 67: 411-443Crossref PubMed Scopus (305) Google Scholar, 4Lee M.G. Ahn W. Choi J.Y. Luo X. Seo J.T. Schultheis P.J. Shull G.E. Kim K.H. Muallem S. J. Clin. Invest. 2000; 105: 1651-1658Crossref PubMed Scopus (58) Google Scholar). Lack of NHE3 activity impairs acid-base balance and extracellular fluid volume homeostasis (5Schultheis P.J. Clarke L.L. Meneton P. Miller M.L. Soleimani M. Gawenis L.R. Riddle T.M. Duffy J.J. Doetschman T. Wang T. Giebisch G. Aronson P.S. Lorenz J.N. Shull G.E. Nat. Genet. 1998; 19: 282-285Crossref PubMed Scopus (708) Google Scholar). Na+/H+ exchanger cAMP-dependent protein kinase cAMP-dependent protein kinase anchoring protein 5-(N-ethyl-N-isopropyl) amiloride PSD-95/discs large/ZO-1 post-confluent day post-synaptic density small interfering RNA cytomegalovirus amino acid(s) express sequence tag Korea Cell Line Bank. NHE3 is known to be regulated by a large variety of hormones, such as α- and β-adrenergic agonists, dopamine, parathyroid hormone, and angiotensin II via multiple signaling systems (6Hu M.C. Fan L. Crowder L.A. Karim-Jimenez Z. Murer H. Moe O.W. J. Biol. Chem. 2001; 276: 26906-26915Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar, 7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar), but the exact underlying mechanisms are still only partially understood. Nevertheless, it has been known for many years that acute regulation of NHE3 activity is linked to protein phosphorylation, as in the case of inhibition by cAMP-dependent protein kinase A (PKA) (7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar, 8Zhao H. Wiederkehr M.R. Fan L. Collazo R.L. Crowder L.A. Moe O.W. J. Biol. Chem. 1999; 274: 3978-3987Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar). Subsequently, it has been demonstrated that adaptor proteins with PDZ (PSD-95/discs large/ZO-1) domains play an important role in the cAMP-dependent inhibition of NHE3 in a number of systems (7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar, 9Ahn W. Kim K.H. Lee J.A. Kim J.Y. Choi J.Y. Moe O.W. Milgram S.L. Muallem S. Lee M.G. J. Biol. Chem. 2001; 276: 17236-17243Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar, 10Donowitz M. Cha B. Zachos N.C. Brett C.L. Sharma A. Tse C.M. Li X. J. Physiol. 2005; 567: 3-11Crossref PubMed Scopus (182) Google Scholar). For example, EBP50 (also known as NHERF1) and E3KARP (also known as NHERF2, SIP-1, or TKA-1) were found to be necessary modular proteins that participated in the cAMP-dependent PKA phosphorylation of NHE3 by forming a multiprotein signaling complex (11Weinman E.J. Steplock D. Wang Y. Shenolikar S. J. Clin. Invest. 1995; 95: 2143-2149Crossref PubMed Scopus (311) Google Scholar, 12Yun C.H. Oh S. Zizak M. Steplock D. Tsao S. Tse C.M. Weinman E.J. Donowitz M. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 3010-3015Crossref PubMed Scopus (404) Google Scholar). In recent years, there has been a growing interest in PDZ domains and modular proteins having PDZ domains. Best studied in the post-synaptic density of PDZ proteins have as a large and important of proteins that of and proteins M. Kim J. Cell Sci. 2000; PubMed Google Scholar, S. S. J. M. Kim J. Biol. Chem. 1999; 274: Full Text Full Text PDF PubMed Scopus Google Scholar, M. Nat. Rev. PubMed Scopus Google Scholar). cells PDZ proteins to the in apical and the PDZ-based protein Shank2 has been to be to the apical of and renal epithelia and the activity of transport and the J.Y. W. W. Lee Kim K.H. H. Kim Lee M.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, L. Biochem. J. PubMed Scopus Google Scholar, Kim M. J. Physiol. 2005; PubMed Scopus Google Scholar). proteins are a family of identified proteins known to as a of membrane protein in M. Kim J. Cell Sci. 2000; PubMed Google Scholar, S. S. J. M. Kim J. Biol. Chem. 1999; 274: Full Text Full Text PDF PubMed Scopus Google Scholar). there are known members of the and found that the PDZ of Shank2 to the of NHE3 in an yeast two-hybrid The to and the and physiological of the between Shank2 and NHE3 using physiological Shank2 the membrane expression and basal activity of NHE3 were increased but the cAMP-dependent inhibition of NHE3 activity was attenuated in the PS120/NHE3 Furthermore, knock-down of native Shank2 expression by RNA interference a in NHE3 activity in Caco-2 epithelial Shank2 to be a protein that NHE3 expression and activity. Cell and cells were in with and The was a at Korea J.A. L.A. J. Physiol. 1999; 276: Google and was a using NHE3 were by to and by an S. P. Pouyssegur J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). The of M. Choi J. Kim S. Lee J. D. M. Kim J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and Kim M. J. Physiol. 2005; PubMed Scopus Google were PS120/NHE3 cells with or W. Kim K.H. Lee J.A. Kim J.Y. Choi J.Y. Moe O.W. Milgram S.L. Muallem S. Lee M.G. J. Biol. Chem. 2001; 276: 17236-17243Abstract Full Text Full Text PDF PubMed Scopus (98) Google using Caco-2 cells were at in a The of and in were used for at and the was on yeast two-hybrid was as M. A. M. 1995; PubMed Scopus Google Scholar). The yeast the and of the was used in the To the activity was by the of yeast growing on the of were amplified by and the The the PDZ domains of and Shank2 were J.Y. W. W. Lee Kim K.H. H. Kim Lee M.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). and of to of Shank2 PDZ and of were and to of were and to were confirmed by sequence proteins were expressed in cells and on and as The proteins were with protein and was as by of A surface plasmon resonance with was used for the of PDZ of at in were at a of 30 The was between using of and were for were by of the by the The were for by the by on were by the and or Caco-2 of were with the and at in were by to protein and with to The or of were in and by The proteins were to and the were by a at in in a and The were with the and and protein were with NHE3 M. J. M. B. Moe O.W. 1995; Full Text PDF PubMed Scopus Google and Shank2 S. P. Pouyssegur J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google were the of was and were S. for and of and the of was in M.G. Schultheis P.J. M. Shull G.E. Tse M. Donowitz M. Muallem S. J. Physiol. 1998; PubMed Scopus Google Scholar, M. J. S. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. R.L. M.C. J. Physiol. 1997; PubMed Google Scholar). and cells were to in The cells were at and in and in The membrane proteins were by the cells in a for 30 the cells were with to and with The cells were and was to the and the was at were and proteins were in by and with NHE3 and the epithelial of Shank2 the of the of protein of number on was using the sequence as a sequence number were by the at the of A of were with protein and with that of were A was used for the of the To the to to the were and were using an using a and a and the whole sequence of was to the with number sequence was to that of a where an is in the to on the of sequence with that of the be in the or in the In a that was to the of in Caco-2 epithelial The were as and The of the and were and The were as and of RNA Shank2 expression in Caco-2 epithelial cells, RNA for were and cells using The small interfering RNA sequence was as cells were used for NHE or in for of Na+/H+ activity was using a with W. Kim K.H. Lee J.A. Kim J.Y. Choi J.Y. Moe O.W. Milgram S.L. Muallem S. Lee M.G. J. Biol. Chem. 2001; 276: 17236-17243Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar). cells on were with a and intracellular were When Shank2 were expressed and a was and were with cells of protein as M.G. W. P.J. Muallem S. J. Biol. Chem. 1999; 274: Full Text Full Text PDF PubMed Scopus Google Scholar). The cells were by an and with an The was in cells to a of with or The and with were by Na+ with The of was to with the was by in to In the a with between and The of PS120/NHE3 cells at was that of Caco-2 cells of the results of NHE activity are expressed as and was for The results are as was using or of A was of Shank2 on cAMP-dependent inhibition of NHE3. and NHE were in PS120/NHE3 cells with or To a basal activity and a large PS120/NHE3 cells were of for and with cells with and are in and of NHE activity and inhibition of NHE activity by cAMP are in A and between Shank2 PDZ and the of has been that the of NHE3 plays an important role in both surface expression and regulation of the activity of NHE3 through with the of family proteins (7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar, 10Donowitz M. Cha B. Zachos N.C. Brett C.L. Sharma A. Tse C.M. Li X. J. Physiol. 2005; 567: 3-11Crossref PubMed Scopus (182) Google Scholar). In a J.Y. W. W. Lee Kim K.H. H. Kim Lee M.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and in for the that and epithelia express PDZ-based adaptor proteins in to family proteins using These and Shank2 that the of NHE3 with PDZ-based in To the between the of NHE3 and the PDZ domains of these adaptor a yeast two-hybrid As in the PDZ of Shank2 a of both and in a interaction between the of NHE3 and the of Shank2. To the interaction between NHE3 and Shank2 in mammalian cells, cells NHE3 were with or with and immunoprecipitation were As in of the expression of Shank2 protein with a of a NHE3 was in the Shank2 cells in a of The between the Shank2 PDZ and the of NHE3 were by surface plasmon resonance As in Shank2 PDZ in to the of and at status was as was a range to that of interaction between the of NHE3 and between Shank2 and NHE3 in the functional of Shank2 on NHE3 the of Shank2 on the surface distribution and activity of NHE3 was In cells that express the of NHE3 protein and proteins were by using of and surface in cells with or with The of NHE3 protein was in the In expression of NHE3 was increased in cells Shank2. NHE3 activity is primarily regulated by the surface expression of NHE3 The results that by the surface distribution of Shank2 the activity of NHE3 (2Zachos N.C. Tse M. Donowitz M. Annu. Rev. Physiol. 2005; 67: 411-443Crossref PubMed Scopus (305) Google Scholar, D. B. P. L. M. Moe O.W. Full Text Full Text PDF PubMed Scopus Google Scholar). To NHE activity in PS120/NHE3 cells was in cells Shank2. NHE activity was as the in intracellular by an as NHE3 in cells have been for NHE3 activity and expression W. Kim K.H. Lee J.A. Kim J.Y. Choi J.Y. Moe O.W. Milgram S.L. Muallem S. Lee M.G. J. Biol. Chem. 2001; 276: 17236-17243Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar). the of NHE3 in the was the of NHE3 expression by the regulation of NHE3 in cells and and surface results in were In that the in NHE3 surface expression of NHE activity are in and and a of results is in the basal NHE activity was increased Shank2 with the results of NHE3 surface In a found that cAMP-dependent inhibitory regulation of NHE3 was partially in cells, in the cells were in to a expression of W. Kim K.H. Lee J.A. Kim J.Y. Choi J.Y. Moe O.W. Milgram S.L. Muallem S. Lee M.G. J. Biol. Chem. 2001; 276: 17236-17243Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar). NHE activity was basal and When the cells were with the cAMP NHE activity was decreased by in PS120/NHE3 cells and a the basal activity Shank2 expression attenuated the cAMP-dependent In PS120/NHE3 cells with cAMP NHE activity by only a in NHE activity with PS120/NHE3 cells regulation of NHE3 renal and epithelia is important in maintaining systemic and homeostasis (2Zachos N.C. Tse M. Donowitz M. Annu. Rev. Physiol. 2005; 67: 411-443Crossref PubMed Scopus (305) Google Scholar, 7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar). the of Shank2 on cAMP-dependent inhibition of NHE3 were further using a In of was to the and was for to basal NHE3 activity as well as to the in basal activity. In the of a of Shank2 that is found in epithelial L. Biochem. J. PubMed Scopus Google Scholar), were cAMP decreased NHE3 activity by in When Shank2 or was cAMP-dependent inhibition of NHE3 activity was attenuated has protein domains in Shank2 there was in to cAMP-dependent inhibition of NHE3 in of Shank2 and NHE3 in Caco-2 the physiological of it is necessary to the of Shank2 on native NHE3 activity in epithelial Caco-2 cells epithelia are known to express and the of using Caco-2 as an in for on of NHE3 have been Tse C.M. A. Donowitz M. J. Physiol. 1999; Google Scholar). Caco-2 cells the and the Korea Cell Line the cells Shank2 expression used of cells for further In NHE3 expression was in Caco-2 cells at post-confluent day and In cells expressed NHE3 and NHE3 protein was the at with protein expression NHE3 activity was in cells at but and of the NHE3 expression is to proteins expressed at the of Caco-2 cells such as and P. J. Cell Physiol. PubMed Scopus Google Scholar). on these the Caco-2 were on or of Shank2 was identified in Caco-2 has been demonstrated that epithelial cells expressed a of and that been identified in L. Biochem. J. PubMed Scopus Google to the of these as using multiple on Caco-2 cells that Caco-2 cells express at and was a of and the sequence of in the number using a and a to and The of of and sequence was to that of the identified in using a and an of in Caco-2 cells and expression of both and in Caco-2 cells was demonstrated by of Caco-2 cells and a to and a to the expressed of both Shank2 proteins When it was found that the of protein was that of in Caco-2 of Shank2 on NHE3 in Caco-2 Shank2 has on RNA interference was used to Shank2 expression in Caco-2 of and of on a effect in Shank2 on was to of at were with the of of and be to an inhibition of in small that to the of of the of S. A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of in Caco-2 cells decreased protein expression of and by and knock-down of Shank2 was by a of NHE3 protein with cells of has been for the knock-down of the expression of a by with Shank2 suggests that the used is for Shank2 In the expression of and were by Shank2 the of Shank2 on NHE3 activity were in Caco-2 NHE3 activity was using to used in PS120/NHE3 cells, that 5-(N-ethyl-N-isopropyl) amiloride was to and that expressed in Caco-2 cells G. S. J. J. Physiol. PubMed Scopus Google Scholar). of NHE activity are in and and of the results are in In with the basal NHE3 activity was Shank2 the cAMP of NHE3 was increased in the Shank2 cells, and the cAMP in the expression of PS120/NHE3 cells it was that Shank2 cAMP signaling on NHE3 activity as well as NHE3 expression in Caco-2 membrane proteins apical and is for and regulated of PDZ-based have as of epithelial that epithelial and transport D. 2000; PubMed Scopus Google Scholar, L. A. A. Cell Biol. 2000; PubMed Scopus Google Scholar). In the a novel interaction between the PDZ-based Shank2 and an epithelial membrane expression and cAMP-dependent regulation of the NHE3 is of membrane Na+/H+ and is by in is expressed on the apical of renal and epithelial Lack of the NHE3 activity impairs acid-base balance and systemic fluid volume homeostasis (5Schultheis P.J. Clarke L.L. Meneton P. Miller M.L. Soleimani M. Gawenis L.R. Riddle T.M. Duffy J.J. Doetschman T. Wang T. Giebisch G. Aronson P.S. Lorenz J.N. Shull G.E. Nat. Genet. 1998; 19: 282-285Crossref PubMed Scopus (708) Google Scholar). hormones, and the signaling systems such as and intracellular have been identified as of NHE3 in and well studied is the (2Zachos N.C. Tse M. Donowitz M. Annu. Rev. Physiol. 2005; 67: 411-443Crossref PubMed Scopus (305) Google Scholar, 7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar). of NHE3 activity by phosphorylation of of NHE3 in and in H. Wiederkehr M.R. Fan L. Collazo R.L. Crowder L.A. Moe O.W. J. Biol. Chem. 1999; 274: 3978-3987Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar), and inhibition only in the of the PDZ-based modular or NHE3 to a protein M. Cha B. Zachos N.C. Brett C.L. Sharma A. Tse C.M. Li X. J. Physiol. 2005; 567: 3-11Crossref PubMed Scopus (182) Google Scholar). has been that both the membrane expression of NHE3 and the of the there have been of the and the (6Hu M.C. Fan L. Crowder L.A. Karim-Jimenez Z. Murer H. Moe O.W. J. Biol. Chem. 2001; 276: 26906-26915Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar, G. Weinman E.J. C.H. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). 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Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). be many for the increased surface of NHE3 by family proteins are known to be in the and of proteins M. Kim J. Cell Sci. 2000; PubMed Google Scholar, M. Nat. Rev. PubMed Scopus Google Scholar). As a the and and of and signaling at the of M. Choi J. Kim S. Lee J. D. M. Kim J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In it was found that Shank2 with a involved in and of membrane trafficking D. J. J. Biol. Chem. 2001; Full Text Full Text PDF Scopus Google Scholar). further the that Shank2 is involved in the trafficking of NHE3 and membrane expression of the in was the decreased NHE3 protein of Shank2 in Caco-2 be that the expression of PS120/NHE3 cells important to epithelial Caco-2 cells were used as a native epithelial to physiological of Shank2 on NHE3 activity. Caco-2 cells, express both Shank2 and are a that have been used to a number of of epithelial cells Tse C.M. A. Donowitz M. J. Physiol. 1999; Google Scholar, P. J. Cell Physiol. PubMed Scopus Google Scholar). Shank2 expression an in the of NHE3 protein in Caco-2 epithelial in the expression of PS120/NHE3 cells, Shank2 an only in the of surface NHE3 The for is that the increased membrane of NHE3 by Shank2 an in the of NHE3 in Caco-2 cells, where NHE3 expression is by an but in PS120/NHE3 cells, where a large of NHE3 is by and a intracellular of NHE3 an is that Shank2 the of NHE3. have been many the of proteins in the regulation of For example, has been to with through and in a T. M. A. M. S. PubMed Scopus Google Scholar). have a with that has been to with and to be involved in regulation D. R. Donowitz M. A. T. Y. J. 2000; 19: PubMed Scopus Google Scholar). The underlying mechanisms for the decreased NHE3 proteins on Shank2 in Caco-2 cells are family of PDZ-based adaptor proteins were identified by and to be an important in the of cells M. Kim J. Cell Sci. 2000; PubMed Google Scholar). In epithelial cells, Shank2 and are expressed in the apical of epithelia J.Y. W. W. Lee Kim K.H. H. Kim Lee M.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, L. Biochem. J. PubMed Scopus Google Scholar, Kim M. J. Physiol. 2005; PubMed Scopus Google Scholar). proteins multiple interaction an a PDZ a and a has protein interaction has only the In the found that both and are in Caco-2 epithelia at an functional assays found in the regulation of by and that the play the role in the of in epithelia and the of the be to the role of The physiological of interaction be Shank2 surface expression of NHE3 and the basal activity of NHE3 in epithelial the that NHE3 is a in the of in epithelia and in the of and in the renal maintaining basal NHE3 activity is important in fluid and acid-base the inhibition of cAMP-dependent signaling on NHE3 by Shank2 has physiological NHE3 is and as of and by In the cAMP-dependent inhibition is in M. Cha B. Zachos N.C. Brett C.L. Sharma A. Tse C.M. Li X. J. Physiol. 2005; 567: 3-11Crossref PubMed Scopus (182) Google Scholar). In an is that Shank2 the of the in the and J.Y. W. W. Lee Kim K.H. H. Kim Lee M.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the both and epithelial in a and by using activity Shank2 epithelial the balance of and cAMP signaling are necessary for regulation of digestive and for has been that NHE3 in large multiprotein in to in X. H. A. S. Y. Donowitz M. J. Physiol. PubMed Scopus Google Scholar). and regulating a balance between cAMP and be a for NHE3 activity. of the that have and Shank2 have been to in renal cells by (7Weinman E.J. Cunningham R. Shenolikar S. Pflugers Arch. 2005; 450: 137-144Crossref PubMed Scopus (40) Google Scholar, Kim M. J. Physiol. 2005; PubMed Scopus Google Scholar). that a in the the the interaction in the role of Shank2 in the regulation of NHE3 activity and expression on the mechanisms by salt and water transport are regulated to systemic and fluid volume at and S. L. Milgram at of for of and S. Muallem at of for and with