KChIP3 Rescues the Functional Expression of Shal Channel Tetramerization Mutants

KChIP proteins regulate Shal, Kv4.x, channel expression by binding to a conserved sequence at the N terminus of the subunit. The binding of KChIP facilitates a redistribution of Kv4 protein to the cell surface, producing a large increase in current along with significant changes in channel gating kinetics. Recently we have shown that mutants of Kv4.2 lacking the ability to bind an intersubunit Zn2+ between their T1 domains fail to form functional channels because they are unable to assemble to tetramers and remain trapped in the endoplasmic reticulum. Here we find that KChIPs are capable of rescuing the function of Zn2+ site mutants by driving the mutant subunits to assemble to tetramers. Thus, in addition to known trafficking effects, KChIPs play a direct role in subunit assembly by binding to monomeric subunits within the endoplasmic reticulum and promoting tetrameric channel assembly. Zn2+-less Kv4.2 channels expressed with KChIP3 demonstrate several distinct kinetic changes in channel gating, including a reduced time to peak and faster entry into the inactivated state as well as extending the time to recover from inactivation by 3–4 fold. KChIP proteins regulate Shal, Kv4.x, channel expression by binding to a conserved sequence at the N terminus of the subunit. The binding of KChIP facilitates a redistribution of Kv4 protein to the cell surface, producing a large increase in current along with significant changes in channel gating kinetics. Recently we have shown that mutants of Kv4.2 lacking the ability to bind an intersubunit Zn2+ between their T1 domains fail to form functional channels because they are unable to assemble to tetramers and remain trapped in the endoplasmic reticulum. Here we find that KChIPs are capable of rescuing the function of Zn2+ site mutants by driving the mutant subunits to assemble to tetramers. Thus, in addition to known trafficking effects, KChIPs play a direct role in subunit assembly by binding to monomeric subunits within the endoplasmic reticulum and promoting tetrameric channel assembly. Zn2+-less Kv4.2 channels expressed with KChIP3 demonstrate several distinct kinetic changes in channel gating, including a reduced time to peak and faster entry into the inactivated state as well as extending the time to recover from inactivation by 3–4 fold. The formation of voltage-gated potassium (Kv) 1The abbreviations used are: Kv, voltage-gated potassium; EGFP, enhanced green fluorescent protein; CHO, Chinese hamster ovary; SEC, size exclusion chromatography; FPLC, fast protein liquid chromatography; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid; ANOVA, analysis of variance. channels is a multistep process with many different interactions and folding events required to form the completed channel (1Deutsch C. Annu. Rev. Physiol. 2002; 64: 19-46Crossref PubMed Scopus (96) Google Scholar). The common functional core of all Kv channels assembles as a tetramer of pore-forming α-subunits. This tetramer is the core of the future ion channel signal transduction complex, but additional folding steps as well as interactions with auxiliary proteins occur before the final functional channel complex at the cell surface is formed. Many auxiliary subunit proteins that bind to Kv α-subunits have been identified, but precisely when these interactions occur during channel complex formation and what role these interactions play in helping the channels to assemble, traffic, and function are topics of great interest (1Deutsch C. Annu. Rev. Physiol. 2002; 64: 19-46Crossref PubMed Scopus (96) Google Scholar, 2Wible B.A. Yang Q. Kuryshev Y.A. Accili E.A. Brown A.M. J. Biol. Chem. 1998; 273: 11745-11751Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar, 3An W.F. Bowlby M.R. Betty M. Cao J. Ling H.P. Mendoza G. Hinson J.W. Mattsson K.I. Strassle B.W. Trimmer J.S. Rhodes K.J. Nature. 2000; 403: 553-556Crossref PubMed Scopus (841) Google Scholar, 4Nadal M.S. Ozaita A. Amarillo Y. de Miera E.V. Ma Y. Mo W. Goldberg E.M. Misumi Y. Ikehara Y. Neubert T.A. Rudy B. Neuron. 2003; 37: 449-461Abstract Full Text Full Text PDF PubMed Scopus (311) Google Scholar). Through the use of heterologous expression systems and mutagenesis studies, we can expose many of these important interactions and folding events, and reveal the processes by which Kv channel complexes form. A comparison of channel expression and functional properties with and without specific auxiliary proteins reveals how these different processes contribute to the formation and function of ion channel complexes. An early step in Kv channel formation involves the tetramerization of the α-subunit T1 domains at the cytoplasmic N terminus of the protein (5Li M. Jan Y.N. Jan L.Y. Science. 1992; 257: 1225-1230Crossref PubMed Scopus (395) Google Scholar, 6Shen N.V. Chen X. Boyer M.M. Pfaffinger P.J. Neuron. 1993; 11: 67-76Abstract Full Text PDF PubMed Scopus (200) Google Scholar, 7Pfaffinger P.J. DeRubeis D. J. Biol. Chem. 1995; 270: 28595-28600Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar). For Kv4.2 channels, a critical component of the T1 domain interaction involves the coordination of an intersubunit Zn2+ ion found on non-Shaker type Kv channel T1 domains (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar, 9Nanao M.H. Zhou W. Pfaffinger P.J. Choe S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 8670-8675Crossref PubMed Scopus (29) Google Scholar, 10Jahng A.W. Strang C. Kaiser D. Pollard T. Pfaffinger P. Choe S. J. Biol. Chem. 2002; 277: 47885-47890Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar). Although Zn2+ binding sites are common in proteins, intersubunit Zn2+ binding sites, as found in the T1 domain, are relatively rare. To determine what functions might by the T1 intersubunit Zn2+ we a of to the Zn2+ coordination and cell surface expression (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). found that to of the Zn2+ binding site a of functional channel expression by subunit This the protein within the endoplasmic reticulum and a in the of subunits on size exclusion to monomeric (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). we can that important function of the Zn2+ site is to channel assembly. functional channels without the Zn2+ we to determine to these mutant channels by with KChIP auxiliary subunit proteins that are known to channel expression by W.F. Bowlby M.R. Betty M. Cao J. Ling H.P. Mendoza G. Hinson J.W. Mattsson K.I. Strassle B.W. Trimmer J.S. Rhodes K.J. Nature. 2000; 403: 553-556Crossref PubMed Scopus (841) Google Scholar). Kv4.2 subunits form channels in the of KChIP auxiliary with KChIP current expression by the trafficking of Kv4 channels K.I. Rhodes K.J. Trimmer J.S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). KChIP auxiliary subunits with Kv4.2 channels by binding to the of the cytoplasmic N terminus and direct binding interactions with the T1 domain W.F. Bowlby M.R. Betty M. Cao J. Ling H.P. Mendoza G. Hinson J.W. Mattsson K.I. Strassle B.W. Trimmer J.S. Rhodes K.J. Nature. 2000; 403: 553-556Crossref PubMed Scopus (841) Google Scholar, W. Y. Kunjilwar K. Pfaffinger P.J. Choe S. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar, K. J. W. Q. W. S. M. M. K. W. Bowlby M.R. P. Rhodes K.J. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar, J. T. D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google the the KChIP subunit is capable of interactions binding to the Kv4 N an and to channel complex W. Y. Kunjilwar K. Pfaffinger P.J. Choe S. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). The KChIP of expression been to a trafficking of channel proteins to to the cell surface W.F. Bowlby M.R. Betty M. Cao J. Ling H.P. Mendoza G. Hinson J.W. Mattsson K.I. Strassle B.W. Trimmer J.S. Rhodes K.J. Nature. 2000; 403: 553-556Crossref PubMed Scopus (841) Google Scholar, K.I. Rhodes K.J. Trimmer J.S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). The redistribution is KChIPs to channel folding of the channels, the of a sequence on Kv4.2 N a surface expression to the channel complex, a of (1Deutsch C. Annu. Rev. Physiol. 2002; 64: 19-46Crossref PubMed Scopus (96) Google Scholar). addition to KChIP binding to the Kv4.2 N terminus the functional gating properties of the The are on the inactivation properties of the channels, KChIP inactivation and the from is an important that channel function at and these channels their current The N terminus of Kv4.2 is in inactivation gating, of on the functional properties of the N terminus that can as a M. J. Full Text PDF PubMed Scopus Google Scholar, M. D. K. B. A. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Jan Y.N. Jan L.Y. Neuron. Full Text PDF PubMed Scopus Google Scholar). the gating changes by KChIPs might on the binding and of the Kv4 N an to a complex of interactions that of the channel M.H. Cao J. K.I. Betty M. P. K.J. Brown D. Y. M. Rhodes K.J. An W.F. Proc. Natl. Acad. Sci. U. S. A. 2002; PubMed Scopus Google Scholar). Here we have KChIP3 binding assembly of the Zn2+ site mutant Kv4.2 subunit proteins by the of channel tetramerization and cell surface function by the complexes as to their assembly and properties in comparison to Kv4.2 with Kv4.2 as a from the Jan The Kv4.2 to a and used to a expression of the T1 domain, as (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). KChIP3 as an and into the as (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google site mutants the and with that in by sequence analysis the from and in with and with as by the with the channel to and to C. J. M. W. S. J. 2003; PubMed Google Scholar). to of the and used a of of site of and of in of which the For the Kv4.2 and KChIP3 used at The Kv4.2 at and at in the of KChIP3 used to the different expression fluorescent protein used as a to the as at For the on the of different KChIP3 the with the mutant to of the of to a Kv4.2 to KChIP3 of we the mutant expression a between type and mutant at significant in the expression with an cell Brown A.M. J. Physiol. 273: PubMed Google Scholar). and by The and The at The at and at an by an on a from with from cell at and at by The with a and on a at in final and on a an as (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). on and to determine the the proteins of and the to the by the time between the and Kv4.2 protein as a on with a of the protein at a in the these and the size to protein that tetrameric in the of the The in the the at the size analysis and are expressed as between of with the and of on The analysis of the to comparison of of to determine a different between mutant and to a different between mutant and mutants changes in the time of used to a channel as inactivation time significant changes with mutant of to and to different from to at The at An with the peak current as and as The the peak current the as the as KChIP3 of Zn2+ interaction of KChIP auxiliary subunits with Kv4.2 α-subunits is an important step in the formation of functional Kv channels W.F. Bowlby M.R. Betty M. Cao J. Ling H.P. Mendoza G. Hinson J.W. Mattsson K.I. Strassle B.W. Trimmer J.S. Rhodes K.J. Nature. 2000; 403: 553-556Crossref PubMed Scopus (841) Google Scholar, K.I. Rhodes K.J. Trimmer J.S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). in the intersubunit interactions of KChIPs might have a direct role in channel assembly their role in channels the cell to we to determine KChIP the of by Zn2+ site assembly mutants of For the in coordination of Zn2+ are and (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). have shown that to these sites functional channel expression by of subunit assembly and of monomeric subunits on (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). For these studies, we have the to to these mutants are by the in the mutants are Zn2+ with a specific to the sites Thus, the and the additional and the additional we have on the lacking all but have and on mutants and of these channels, and found that they from Kv4.2 expression in the mutant functional expression without KChIP and C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). of KChIP3 at a Kv4.2 a large increase in functional with KChIP3 mutant producing functional the of current is of that with Kv4.2 channels with several Zn2+ site and the are in Although of the Zn2+ mutants without they all to a of when with KChIP3 at a Zn2+ site functional peak current expression with of KChIP3 with different Zn2+ site mutants of Kv4.2 in at by cell size as by cell shown all with and without KChIP3 Kv4.2 functional current without Zn2+ site mutants to a of expression of that with Kv4.2 with A of function is with of these mutants with type that expression of all mutants reduced with A between the mutants significant between expression of different KChIP3 increase in current expression is with expressed with a of channel and of KChIP3 The of in all Kv4.2 peak with KChIP3 at the of channel the of expression the KChIP3 is channel to the and the Kv4.2 and The KChIP3 expression of the mutant is significant between the mutant and A on the a significant between mutant and To determine reduced expression enhanced with of KChIP3 we the KChIP3 to Kv4.2 and these in Kv4.2 expression the current is the of functional expression with channels KChIP3 to Zn2+ that is a distinct KChIP3 of Kv4.2 channels To we the channel and the of KChIP3 the of the of a different of Kv4.2 and KChIP3 significant in current are with a of KChIP3 to Kv4.2 a the of expression is and in current are with of KChIP3 The KChIP3 is by of protein with the of the channel the is with additional KChIP required current expression of channels with a of KChIP3 to at a of with current at KChIP3 to functional expression to channels at a KChIP3 to Kv4.2 of the the of protein the in the with that a is KChIP3 binding to Zn2+ site mutant channel subunits is driving functional expression of these that the of function by Zn2+ site is a specific in the assembly of the channel a of the subunit and that the of KChIP3 is to assembly (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar, 10Jahng A.W. Strang C. Kaiser D. Pollard T. Pfaffinger P. Choe S. J. Biol. Chem. 2002; 277: 47885-47890Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar). To we to determine the assembly state of the channel KChIP3 of Zn2+ have shown that the subunit protein as a on with the tetrameric of the channel (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). to the that KChIP3 rescuing the function of by driving tetramer with KChIP3 and with without Zn2+ site and the proteins and the channel assembly state by the of Kv4.2 in with into is found in size with and C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). of Kv4.2 with the channel in the tetrameric KChIP3 is found to with the channel in addition to the a into the channel complex Although KChIP addition is to increase the channel protein by large in the of the channel protein in the that KChIP3 is into the and the from on Kv4.2 channels with the is found to with the T1 domain and the cytoplasmic terminus J. D. M.H. S. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). For the of a channel complex with KChIP3 are is found in the monomeric with KChIP3 at a a redistribution of tetrameric and monomeric channel protein is on the KChIP is to the of the to tetramer is with all protein found in the tetrameric in on assembly state well with the expression KChIP3 of KChIP3 is into the channel complex with tetrameric the of the KChIP3 protein is found in the KChIP as with of the with several Zn2+ site mutant that of KChIP3 with mutant channels at a in channel protein from to tetramer that the of KChIP3 in the of mutants an assembly and the subunits to tetramer in the of the Zn2+ binding interactions that the T1 tetrameric of Zn2+ of the by have shown that KChIP3 the function of Zn2+ binding site mutants by driving the assembly of these subunits to that in the of KChIP3 the Zn2+ site mutant channel protein from the endoplasmic reticulum to trafficking to the cell For these we have used are large that a of the systems of the we the of Kv4.2 in in the of the protein is in endoplasmic reticulum and as can by within the systems of the cell (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar, K.I. Rhodes K.J. Trimmer J.S. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). of of KChIP3 Kv4.2 protein of these producing a the as proteins the surface of these we a cell that subunits to channels, the Zn2+ site mutant channels are (8Strang C. Kunjilwar K. DeRubeis D. Peterson D. Pfaffinger P.J. J. Biol. Chem. 2003; 278: 31361-31371Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). For addition of of KChIP3 to the the protein with a of KChIP3 the protein is from the and a to channels of Zn2+-less Kv4 ability to function by with KChIP3 with an to the changes in channel functional properties without Zn2+ to the Kv4.2 T1 we unable to without KChIP we on the of how the by of KChIP3 and are different from channels by of KChIP3 and we have current Kv4.2 and with KChIP3 in to steps from to The are to the peak and the to a comparison of the and mutant The that is is that the the mutant channels have Zn2+ site mutants and find to a of these of Zn2+ binding the inactivation of channels during A is by of the in to the shown to which a of current channels channels of the at that the their and before Kv4.2 the state inactivation and peak properties and Zn2+ site mutant state inactivation and Zn2+ mutant channels in the of For the the inactivation in the of For at an enhanced to these mutant and Zn2+ mutant Kv4.2 channels expressed in the of KChIP3 The of Kv4.2 channels is with the mutant The of channels a of with Kv4.2 channels expressed with these on are is a significant in the between and inactivation mutants The channels is to a of current between and the kinetic in the current that these in function between Kv4.2 channels and channels expressed with we the time to peak and the inactivation kinetics. For the time required to peak the channel faster at the time to peak channels with the changes in inactivation that the current in Zn2+ site mutant Kv4 channel inactivation been in into and inactivation M. J. Full Text PDF PubMed Scopus Google Scholar, M. M. J. Physiol. PubMed Scopus Google Scholar, A. M. J. Physiol. PubMed Scopus Google Scholar). state inactivation a by the Kv4 cytoplasmic N terminus and is by of the Kv4 N terminus binding of KChIP proteins to the N terminus M. D. K. B. A. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Bowlby M. An W.F. Rhodes K.J. M. J. Physiol. 2002; PubMed Scopus Google Scholar). state inactivation is a process from state to state state inactivation is by of the Kv4 inactivation A. M. J. Physiol. PubMed Scopus Google Scholar). Although the inactivation is is to within the channel and in an between and channel M. M. J. Physiol. PubMed Scopus Google Scholar, A. M. J. Physiol. PubMed Scopus Google Scholar, Bowlby M. An W.F. Rhodes K.J. M. J. Physiol. 2002; PubMed Scopus Google Scholar, M. J. Full Text Full Text PDF PubMed Scopus Google Scholar). A inactivation process with Kv4 channels that is with and is to a distinct process from inactivation in the inactivation is A. M. J. Physiol. PubMed Scopus Google Scholar). the of the of the current and Zn2+ site mutants can as well as the of The faster process is to by the entry of Kv4.2 channels into state and the process is by into the inactivated state M. D. K. B. A. J. Full Text Full Text PDF PubMed Scopus Google Scholar, Bowlby M. An W.F. Rhodes K.J. M. J. Physiol. 2002; PubMed Scopus Google Scholar). these we that of the Zn2+ site the of inactivation as well as the of the the faster kinetic and all to the of the mutant the in state inactivation by Zn2+ site we to the time entry into the inactivated state as well as the time the from For Kv4 channels, the inactivation at the state is by entry into the state inactivation because at channel M. M. J. Physiol. PubMed Scopus Google Scholar, A. M. J. Physiol. PubMed Scopus Google Scholar, M. J. Full Text Full Text PDF PubMed Scopus Google Scholar). we the inactivation type as well as Zn2+ mutant channels expressed with KChIP3 at the state we the state inactivation of Kv4.2 expressed with with an of the state inactivation of channels with KChIP3 in to the inactivation from the in state the channels Kv4.2 channels when to the are in inactivation to the that the inactivation of these between and channels is The is that Zn2+ mutant channels the of inactivation at as from the in state The is that the entry into the inactivated state are different between and Zn2+ mutant channels, to the the Zn2+ mutant channels to a state the entry into the inactivated state and Zn2+ site mutant have the and the to at different the inactivation of channels is that Kv4.2 of the channels a and the at inactivation of channels is in with on shown in from of state inactivation is by the of the entry into the inactivated state to the of from the inactivated in changes in the from of a inactivated are with the of the Zn2+ a the time at the to the time A and the Kv4.2 and The of the peak and the time at the and channels in is from these that the mutants recover from For Kv4.2 expressed with the time to recover from inactivation at is the is to is as as Kv4.2 expressed without of the Zn2+ site of the that KChIP3 to the of Kv4.2 from the from a of between and that the of is these studies, we have found that the KChIP3 auxiliary subunit protein a ability to the function of an assembly of Kv4.2 subunit Kv4.2 subunits with the site are unable to form functional channels because of a of subunit that of function in these mutants is a specific to the of Zn2+ a of these mutants to Zn2+ coordination and have on channel assembly and have functional changes when by The coordination are in different The coordination is found on the surface and the folding and interaction of the assembly M.H. Zhou W. Pfaffinger P.J. Choe S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 8670-8675Crossref PubMed Scopus (29) Google Scholar). The between these mutants is that they all Zn2+ binding to KChIPs are to in the assembly of capable of binding to subunits and driving to form functional important into KChIP The by which KChIPs are to channel assembly is KChIP proteins have been shown to bind to the of Kv4.2 subunits W. Y. Kunjilwar K. Pfaffinger P.J. Choe S. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). is that the the T1 domain and the KChIP protein to with and the assembly with the Zn2+ site a is by which have shown that KChIP proteins can with specific of the T1 domain, a direct to interactions K. J. W. Q. W. S. M. M. K. W. Bowlby M.R. P. Rhodes K.J. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). have a binding of KChIPs along the T1 interaction J. D. M.H. S. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). with in that a on KChIP binding on the of the the KChIP protein is into the channel The of the interaction driving assembly by the interactions between KChIPs to the Kv4.2 N terminus W. Y. Kunjilwar K. Pfaffinger P.J. Choe S. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). This the interactions within the T1 domain, but the with a of interactions that occur from the T1 mutagenesis that can KChIP interactions from direct KChIP interactions with the T1 domain to between these different important to is the of KChIPs driving subunit assembly with their trafficking properties in the formation of Although that to in Kv4.2 subunit assembly without in Kv4.2 expression is by a the assembly of Kv4 channels into a tetrameric channel auxiliary subunits to the channel to find the required subunits of the of of proteins at the we a when we trafficking and assembly into of that the of and Zn2+ site mutant channels are in the of Thus, processes that the Zn2+ site mutant channel proteins within the endoplasmic reticulum are the protein as an interaction with KChIP the assembly and the protein to the cell on and have that formation of functional in these interactions with auxiliary subunits as KChIP3 Pfaffinger P.J. M. and PubMed Scopus Google Scholar, M. Y. Y. J. Full Text Full Text PDF PubMed Scopus Google Scholar, C. J. M. W. S. J. 2003; PubMed Google Scholar). in these processes distinct functional to determine to KChIPs can identified, which their ability to Zn2+ site mutant Kv4 channel assembly without channel trafficking and that an Zn2+ binding site of Kv4.2 subunits is required channel For Kv4.2 channels, the of Zn2+ site is a from inactivation by the time is is by the from and is a that the of the inactivated state of the channel by Zn2+ site at we find that the Zn2+ site mutant channels peak and have that inactivation in Kv4 channels is by the channels in the inactivated state at and A. M. J. Physiol. PubMed Scopus Google Scholar). The of the inactivated state by Zn2+ site mutagenesis is to the of inactivation at Kv4.2 channels from the inactivated An the reduced time to peak and faster inactivation is that Zn2+ site the entry into the inactivated The of these to the state inactivation Zn2+ site mutant Zn2+ site mutants inactivation by different the to the inactivated the of channels that remain on channels that of the to channel Brown A.M. J. Physiol. 273: PubMed Google Scholar). Although the identified, the the that form the T1 Zn2+ a on gating is in Kv4.2 channels with Zn2+ site the of state inactivation of Kv4.2 Although a time to to to the reduced time to peak in Zn2+ site mutant Kv4.2 channels, the inactivation of these channels in the process and the of faster To the of these different of channel of and Zn2+ site mutant Jan with the Kv4.2