Key points are not available for this paper at this time.
Plasma membrane Ca2+-ATPases (PMCAs) are involved in local Ca2+ signaling and in the spatial control of Ca2+ extrusion, but how different PMCA isoforms are targeted to specific membrane domains is unknown. In polarized MDCK epithelial cells, a green fluorescent protein-tagged PMCA4b construct was targeted to the basolateral membrane, whereas a green fluorescent protein-tagged PMCA2b construct was localized to both the apical and basolateral domain. The PDZ protein-binding COOH-terminal tail of PMCA2b was not responsible for its apical membrane localization, as a chimeric pump made of an NH2-terminal portion from PMCA4 and a COOH-terminal tail from PMCA2b was targeted to the basolateral domain. Deletion of the last six residues of the COOH terminus of either PMCA2b or PMCA4b did not alter their membrane targeting, suggesting that PDZ protein interactions are not essential for proper membrane localization of the pumps. Instead, we found that alternative splicing affecting the first cytosolic loop determined apical membrane targeting of PMCA2. Only the “w” form, which contains a 45-amino acid residue insertion, showed prominent apical membrane localization. By contrast, the x and z splice variants containing insertions of 14 and 0 residues, respectively, localized to the basolateral membrane. The w splice insert was the crucial determinant of apical PMCA2 localization, and this was independent of the splice configuration at the COOH-terminal end of the pump; both PMCA2w/b and PMCA2w/a showed prominent apical targeting, whereas PMCA2x/b, PMCA2z/b, and PMCA2z/a were confined to the basolateral membrane. These data report the first differential effect of alternative splicing within the first cytosolic loop of PMCA2 and help explain the selective enrichment of specific PMCA2 isoforms in specialized membrane compartments such as stereocilia of auditory hair cells. Plasma membrane Ca2+-ATPases (PMCAs) are involved in local Ca2+ signaling and in the spatial control of Ca2+ extrusion, but how different PMCA isoforms are targeted to specific membrane domains is unknown. In polarized MDCK epithelial cells, a green fluorescent protein-tagged PMCA4b construct was targeted to the basolateral membrane, whereas a green fluorescent protein-tagged PMCA2b construct was localized to both the apical and basolateral domain. The PDZ protein-binding COOH-terminal tail of PMCA2b was not responsible for its apical membrane localization, as a chimeric pump made of an NH2-terminal portion from PMCA4 and a COOH-terminal tail from PMCA2b was targeted to the basolateral domain. Deletion of the last six residues of the COOH terminus of either PMCA2b or PMCA4b did not alter their membrane targeting, suggesting that PDZ protein interactions are not essential for proper membrane localization of the pumps. Instead, we found that alternative splicing affecting the first cytosolic loop determined apical membrane targeting of PMCA2. Only the “w” form, which contains a 45-amino acid residue insertion, showed prominent apical membrane localization. By contrast, the x and z splice variants containing insertions of 14 and 0 residues, respectively, localized to the basolateral membrane. The w splice insert was the crucial determinant of apical PMCA2 localization, and this was independent of the splice configuration at the COOH-terminal end of the pump; both PMCA2w/b and PMCA2w/a showed prominent apical targeting, whereas PMCA2x/b, PMCA2z/b, and PMCA2z/a were confined to the basolateral membrane. These data report the first differential effect of alternative splicing within the first cytosolic loop of PMCA2 and help explain the selective enrichment of specific PMCA2 isoforms in specialized membrane compartments such as stereocilia of auditory hair cells. plasma membrane Ca2+-ATPases Madin-Darby canine kidney green fluorescent protein 4′,6′-diamidino-2-phenylindole Na+/H+ exchanger regulatory factor-2 Dulbecco's phosphate-buffered saline Ca2+/Mg2+ Plasma membrane Ca2+-ATPases (PMCAs)1 constitute the major high affinity Ca2+ extrusion system of eukaryotic cells. Their function is crucial for the maintenance of the normally low cytosolic free Ca2+ levels (Ca2+i) in resting cells and to counteract the transient increases in Ca2+i generated during Ca2+signaling (1Carafoli E. Physiol. Rev. 1991; 71: 129-153Crossref PubMed Scopus (578) Google Scholar, 2Strehler E.E. Zacharias D.A. Physiol. Rev. 2001; 81: 21-50Crossref PubMed Scopus (484) Google Scholar). The spatially and temporally distinct demands on Ca2+ influx and efflux mandate the proper spatial distribution and abundance of the PMCAs across the plasma membrane. This is of particular importance in polarized cells such as neurons or epithelial cells where Ca2+ signaling often must be restricted to the pre- and post-synaptic membrane (neurons) or where Ca2+ influx and efflux must be spatially segregated between the apical and basolateral membrane (Ca2+ transporting epithelia). However, the molecular determinants and the mechanisms by which PMCAs are targeted to distinct membrane domains are unknown. Mammalian PMCAs are encoded by four separate genes giving rise to PMCA isoforms 1–4. Isoform complexity is further enhanced by alternative splicing of the primary transcripts, such that over 20 distinct PMCA variants exist in the mammalian proteome (2Strehler E.E. Zacharias D.A. Physiol. Rev. 2001; 81: 21-50Crossref PubMed Scopus (484) Google Scholar). Alternative splicing affects two major regions of the protein (splice sites A and C): the first intracellular loop between membrane-spanning domains 2 and 3, and the COOH-terminal tail which corresponds to a major regulatory region of the pump and contains its calmodulin-binding site (Fig.1). Alternative splicing at site A does not change the overall reading frame of the pump; instead, varying numbers of amino acids (from 14 to 45 in human PMCA2) are optionally inserted into the intracellular loop separating membrane-spanning segments 2 and 3 (Fig. 1). Splicing at site A is most complex in PMCA2 where the optional insertion of three separate exons leads to splice variant 2w (all three exons included), 2x (only the third exon included), 2y (only the first two exons included), and 2z (none of the alternative exons included) (2Strehler E.E. Zacharias D.A. Physiol. Rev. 2001; 81: 21-50Crossref PubMed Scopus (484) Google Scholar). The functional effect of alternative splicing at site A is unknown, although it has been noted that the changes occur close to a phospholipid-binding domain of the pump (3Adamo H.P. Penniston J.T. Biochem. J. 1992; 283: 355-359Crossref PubMed Scopus (41) Google Scholar, 4Heim R. Hug M. Iwata T. Strehler E.E. Carafoli E. Eur. J. Biochem. 1992; 205: 333-340Crossref PubMed Scopus (54) Google Scholar). The first intracellular loop also participates in the pump mechanism as the so-called A (actuator) domain (5Toyoshima C. Nakasako M. Nomura H. Ogawa H. Nature. 2000; 405: 647-655Crossref PubMed Scopus (1609) Google Scholar). The main splice variants (termed “a” and “b”) generated at the COOH-terminal site differ in their primary amino acid sequence due to a change in reading frame. Functionally, the most notable consequence of COOH-terminal splicing is a difference in calmodulin regulation of the respective pump variants (2Strehler E.E. Zacharias D.A. Physiol. Rev. 2001; 81: 21-50Crossref PubMed Scopus (484) Google Scholar, 6Penniston J.T. Enyedi A. J. Membr. Biol. 1998; 165: 101-109Crossref PubMed Scopus (158) Google Scholar). In addition, the extreme COOH-terminal sequence of the b splice variants (but not of the a-forms) has been shown recently to interact with several PDZ proteins including members of the synapse-associated protein family (7DeMarco S.J. Strehler E.E. J. Biol. Chem. 2001; 276: 21594-21600Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar), NO synthase I (8Schuh K. Uldrijan S. Telkamp M. Röthlein N. Neyses L. J. Cell Biol. 2001; 155: 201-205Crossref PubMed Scopus (133) Google Scholar), and Na+/H+ exchanger regulatory factor-2 (NHERF2) (9DeMarco S.J. Chicka M.C. Strehler E.E. J. Biol. Chem. 2002; 277: 10506-10511Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). Differential interaction with specific PDZ proteins may be one mechanism for the membrane targeting or retention of specific transporters or receptors. We recently reported (7DeMarco S.J. Strehler E.E. J. Biol. Chem. 2001; 276: 21594-21600Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar) that PMCA4b is almost exclusively localized in the basolateral membrane of polarized Madin-Darby canine kidney (MDCK) epithelial cells where it may interact with the PDZ protein synapse-associated protein 97. By contrast, we found that a GFP-tagged PMCA2b isoform was mainly targeted to the apical membrane where it co-localized with NHERF2 as a specific interaction partner (9DeMarco S.J. Chicka M.C. Strehler E.E. J. Biol. Chem. 2002; 277: 10506-10511Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). Here we first set out to test the hypothesis that alternative splicing affecting the COOH-terminal tail may lead to differential membrane targeting of PMCAs. By using recombinant protein expression and confocal fluorescence microscopy, we find that the PDZ binding tail is dispensable for basolateral or apical membrane targeting, suggesting that COOH-terminal splicing plays no primary role for the proper localization of PMCA isoforms. Surprisingly, however, alternative splicing at site A influences apical or basolateral localization of PMCA2. PMCA2w, but not -2x or -2z, is targeted to the apical membrane, and this is true regardless of whether the COOH-terminal splice corresponds to the a or b variant. Our data suggest for the first time a role for alternative splicing at site A of PMCA2, indicating the importance of this splicing event for differential membrane targeting of the calcium pump in polarized cells. GFP-PMCA4b encoding human PMCA4x/b fused at its NH2 terminus to GFP was generated by cloning an XhoI fragment carrying the full-length PMCA4x/b sequence into pEGFP-C2 (Clontech). The PMCA4x/b sequence was PCR-amplified using pMM2-PMCA4b (3Adamo H.P. Penniston J.T. Biochem. J. 1992; 283: 355-359Crossref PubMed Scopus (41) Google Scholar) as template together with primers 4b-start (5′-ggg ggctcgaga acg aac cca tca gac cgt gtc ttg cc-3′) and 4b-stop (5′-ccc cctcga gtc aaa ctg atg tct cta ggc tct gta g-3′) containingXhoI recognition sequences (underlined). The full-length coding sequence of PMCA2x/b was first assembled as a NotI fragment in pBluescript-KS using reverse transcriptase-PCR and cDNAs cloned previously (4Heim R. Hug M. Iwata T. Strehler E.E. Carafoli E. Eur. J. Biochem. 1992; 205: 333-340Crossref PubMed Scopus (54) Google Scholar). To generate full-length cDNAs for PMCA2w/b and PMCA2z/b, a BstEII-SphI fragment encompassing the alternative splice site A region in PMCA2x was replaced by corresponding cassettes containing the 2w and 2z sequence, respectively. The NotI fragments carrying the full-length PMCA2w/b, -2x/b, or -2z/b coding sequence were then excised from pBluescript-KS and subcloned into the NotI site of pSPORT-1 (Invitrogen). Finally, the PMCA2 sequences were cloned asMluI-SalI (2w/b and 2x/b) orMluI-KpnI fragments (2z/b) into the modified pMM2 expression vector (3Adamo H.P. Penniston J.T. Biochem. J. 1992; 283: 355-359Crossref PubMed Scopus (41) Google Scholar) to generate pMM2-PMCA2w/b, pMM2-PMCA2x/b, and pMM2-PMCA2z/b. To create constructs for GFP-PMCA2w/b and GFP-PMCA2x/b, the full-length PMCA2w/b and PMCA2x/b sequences were released as SacII/XbaI fragments from the original pBluescript-KS vectors and cloned into a modified pEGFP-C1 expression vector (Clontech) containing consecutive hemagglutinin and His6 tags Strehler E.E. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar) between the GFP and the respective PMCA To constructs and a previously (9DeMarco S.J. Chicka M.C. Strehler E.E. J. Biol. Chem. 2002; 277: 10506-10511Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar) was as it to a an fragment encoding the COOH-terminal residues was replaced by a corresponding fragment carrying a six residues of the original fragment containing the NH2-terminal was then excised from this and replaced by corresponding fragments from GFP-PMCA2w/b and to create the constructs and respectively. The expression vector has been previously Enyedi A. Penniston J.T. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The expression vector was generated by a pMM2 an fragment from GFP-PMCA2w/b the end coding sequence including the “w” insert at splice site and an fragment from the region and sequence at splice site The chimeric PMCA construct was made by an fragment the COOH-terminal residues from to in GFP-PMCA4b with a fragment the corresponding COOH-terminal sequence from (9DeMarco S.J. Chicka M.C. Strehler E.E. J. Biol. Chem. 2002; 277: 10506-10511Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). The construct a GFP-tagged chimeric PMCA of residues of PMCA4 splice fused to the COOH-terminal residues of PMCA2 splice The of constructs was by in the A of constructs is shown in cells were to on in Dulbecco's modified with amino and (all from were with 2 of using to the (Invitrogen). the cells were as (7DeMarco S.J. Strehler E.E. J. Biol. Chem. 2001; 276: 21594-21600Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar), and the protein in the determined by the of the from and cells were on and to R. K. in Scholar). were in of the PMCAs using specific and were from Penniston and and at of and respectively. or to were from and at with primary and and of the was as previously Strehler E.E. J. 2001; PubMed Scopus Google Scholar). I MDCK epithelial cells were to on in Dulbecco's modified containing were with a of 2 of using (Invitrogen). the cells were for at in in Ca2+/Mg2+ in were further and in for at The cells were in containing and and were then for at with or 3 for in the cells were for at with the or to or The were at a of and for were in was also to the at a of 20 to were in were on a using an and using were and using MDCK cells were to as a on with PMCA2 expression constructs and for as using and by and respectively. were on a as of the apical most of 20 cells from were the and and for within the frame and using an from two By using the an was that a of the apical of of the of the apical domain as the of the This was then on the apical domain of the apical in to the fluorescence the green for of the 20 from of the different a that most of the membrane is essential as it an of the apical domain as a and as with high or low abundance of apical protein that the overall for a then be by a to the apical fluorescence of that These numbers were to construct a the for of the 20 cells from a and were also in a the of the 20 fluorescence for of the PMCA2 We noted previously that PMCA4b was almost exclusively in the basolateral membrane of polarized MDCK cells (7DeMarco S.J. Strehler E.E. J. Biol. Chem. 2001; 276: 21594-21600Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar, Strehler E.E. J. Physiol. PubMed Scopus Google Scholar), whereas a of GFP-tagged PMCA2b was found at the apical membrane where it co-localized with its binding partner NHERF2 (9DeMarco S.J. Chicka M.C. Strehler E.E. J. Biol. Chem. 2002; 277: 10506-10511Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). To that the difference in membrane targeting is not due to the GFP we GFP-PMCA4b in MDCK cells and its localization to that of GFP-tagged proteins were in cells as determined by using in polarized Madin-Darby canine kidney cells, GFP-PMCA4b was targeted to the basolateral membrane whereas the construct was at the apical membrane in to the basolateral membrane (Fig. the difference in membrane localization of two PMCA isoforms is not due to the of the GFP at their membrane localization of PMCA isoforms. GFP-tagged PMCA4b and PMCA2b constructs were in MDCK cells, and their localization was determined by confocal fluorescence is localized to the membrane of at with no of the apical membrane The basolateral localization of the GFP-PMCA4b isoform is from the shown the GFP-PMCA2w/b prominent apical localization apical in to The apical and localization of this isoform is in the on the where the apical and were for the were with in in in in and in in A and PMCA b splice variants interact with several PDZ proteins but also specific PDZ protein (7DeMarco S.J. Strehler E.E. J. Biol. Chem. 2001; 276: 21594-21600Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar, S.J. Chicka M.C. Strehler E.E. J. Biol. Chem. 2002; 277: 10506-10511Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). but not to NHERF2 which is a of a of PDZ proteins involved in membrane and regulation of transporters and including S. J. PubMed Scopus Google Scholar), J.T. A. S. S. Nature. 1998; PubMed Scopus Google Scholar), and the A. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, S. M. 1998; PubMed Scopus Google Scholar). The differential localization of PMCA2b and PMCA4b be different interactions by their COOH-terminal To test this we generated a chimeric construct in which the GFP-PMCA4b COOH-terminal tail of residue was replaced by the corresponding tail of in polarized MDCK cells, the localization of this was from the chimeric pump was exclusively found in the basolateral membrane (Fig. the of the PMCA2b does not apical targeting on a chimeric protein with its NH2-terminal from PMCA2 and PMCA4 differ at sequence their overall to the most between isoforms at splice site A. we noted that targeted GFP-PMCA4b construct to the whereas the targeted construct to the for a of the splice To test the splice site A configuration be involved in the different membrane targeting, we expression vectors for of the human splice site A variants of -2x/b, and -2z/b (Fig. To out effect of the NH2-terminal GFP vectors were made to the full-length PMCA2 of of from cells showed that constructs were at levels (Fig. in polarized MDCK cells, PMCA2x/b and were localized in the basolateral membrane (Fig. and whereas PMCA2w/b showed prominent apical localization in to basolateral This difference in membrane localization was by confocal at different of the cells and is in the shown in three constructs to the b splice variant at their COOH-terminal end and are for the insertion of 45 14 or 0 amino acid residues in their first intracellular the in membrane localization must be due to the changes that at splice site to the insertion of residues in the w splice The using a chimeric construct shown that the COOH-terminal tail is not the major determinant for apical basolateral targeting of the PMCAs. However, the of a functional sequence may be for membrane targeting of the pumps. To test this is the we GFP-PMCA2w/b and constructs their six COOH-terminal residues 2 and to interact with PDZ shown in and were targeted to the apical and basolateral respectively, as from their splice site A was targeted to the basolateral membrane as been for the corresponding full-length PMCA4x/b isoform (Fig. We that a functional domain at the COOH terminus is not for targeting of the PMCAs and that PDZ protein interactions are dispensable for the to their membrane the insertion of the amino acids of the w splice variant were a major determinant of apical targeting of PMCA2, we w variants to be targeted to the apical membrane of the splice configuration at their COOH To test this we generated expression vectors for full-length PMCA2w/a and PMCA2z/a 2 and constructs were into MDCK cells, PMCA2z/a localized to the basolateral membrane, whereas PMCA2w/a showed prominent apical localization the targeting of PMCA2w/a and PMCA2z/a is to that of PMCA2w/b and PMCA2z/b, respectively. To a of the targeting of the different splice site A we determined the apical membrane fluorescence in cells with either PMCA2w/b, or as A of the fluorescence in a of the apical membrane is shown in for 20 cells from and the apical fluorescence for PMCA2 construct is in The data the localization of PMCA2x/b, and in the apical membrane, in to the of PMCA2w/b and in this membrane The also that PMCA2w/b and PMCA2w/a are in the apical membrane, further the primary importance of the w splice configuration in PMCA2 membrane of apical membrane fluorescence of PMCA2 splice site A variants in cells. MDCK cells were with PMCA2w/b, -2x/b, or and with by were the confocal fluorescence and were of apical membrane of cells. The fluorescence was determined as and the data for 20 cells from are in The apical fluorescence for PMCA2 construct was from the data in A and is in the apical fluorescence for PMCA2w/b and PMCA2w/a with the almost apical fluorescence for PMCA2x/b, and The data in fluorescence and spatially segregated changes in Ca2+ the for the of intracellular Ca2+ This is and expression of an of Ca2+ and signaling Rev. Cell Biol. 2000; PubMed Scopus Google J. Cell 2001; PubMed Google Scholar). the PMCAs are to be responsible for the maintenance of the low resting data suggest that in local and help the and of Ca2+ (8Schuh K. Uldrijan S. Telkamp M. Röthlein N. Neyses L. J. Cell Biol. 2001; 155: 201-205Crossref PubMed Scopus (133) Google Scholar, S.J. C. Strehler E.E. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. 2001; PubMed Google Scholar, J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, Enyedi Penniston J.T. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar). PMCA isoforms and splice variants are and localized in several and auditory and hair cells of the almost exclusively in their apical In the basolateral membrane, cells mainly Penniston J.T. J. 2001; PubMed Google Scholar). in the of the is in the and of but from the and PMCA2 is in the membrane of cells in the S.J. J. Strehler E.E. J. 2002; PubMed Scopus Google Scholar). Differential localization in distinct membrane domains may be one of the PMCA isoforms and splice the most difference between PMCA splice variants between the a and b COOH-terminal splice it was to that their different the for differential membrane the b variants are to interact with PDZ domains (7DeMarco S.J. Strehler E.E. J. Biol. Chem. 2001; 276: 21594-21600Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar, E. S.J. M. Strehler E.E. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar), and PDZ protein interactions been shown to be involved in the targeting, of several membrane and Cell Biol. PubMed Scopus Google Scholar, M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar). to with the and transporters J. S. M. M. J. PubMed Scopus Google Scholar, C. A. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, 1998; Full Text Full Text PDF PubMed Scopus Google Scholar), that the targeting of PMCAs in polarized MDCK cells is independent of their splice site configuration and does not a functional COOH-terminal Instead, we an role for changes at splice site A in PMCA2 variants to the apical basolateral membrane. Only the variant with the insert of 45 residues was whereas PMCA2x and amino acids were localized in the basolateral membrane. The importance of the splice site A configuration for targeting of PMCA2 is by isoform and localization The apical membrane of auditory and hair cells is for the PMCA2w/a variant Penniston J.T. J. 2001; PubMed Google Scholar). In PMCA2 is also at high levels in the apical membrane of epithelial cells where it is to an essential role in Ca2+ into the In this the splice corresponds to PMCA2w/b J. Physiol. 276: PubMed Google Scholar, Penniston J.T. J. Physiol. 2000; PubMed Google Scholar). in both where PMCA2 apical localization in polarized its splice configuration corresponds to the w variant at site A. By contrast, the splice site configuration to be of importance as it is a in one but b in the Penniston J.T. J. 2001; PubMed Google Scholar) recently a PMCA2 splice site A variant in the apical stereocilia of hair cells. This an insert of amino of the 45 residues found in the w variant and an residues encoded by a separate In however, a PMCA2 splice site A variant corresponding to has been Our the spatial of mechanisms at the plasma membrane is the molecular of the two major the PMCAs and the has over the last in 2Strehler E.E. Zacharias D.A. Physiol. Rev. 2001; 81: 21-50Crossref PubMed Scopus (484) Google Scholar, E. J. PubMed Scopus Google Scholar, and Physiol. Rev. PubMed Scopus Google Scholar), the mechanisms by which proteins are targeted to specific membrane domains and assembled into functional with Ca2+signaling to be the w insert at splice site A alter the membrane targeting of different but not are as a change in the interaction of the pump with specific and a difference in the splice site A insert is NH2-terminal to a region in the first cytosolic loop of the pump R. T. Carafoli E. Eur. J. Biochem. 1992; PubMed Scopus Google Scholar) 1). The amino acids of the w splice may alter the of the region membrane-spanning domains to their interaction with in apical The w insert is in and as as in and residues (3Adamo H.P. Penniston J.T. Biochem. J. 1992; 283: 355-359Crossref PubMed Scopus (41) Google Scholar, 4Heim R. Hug M. Iwata T. Strehler E.E. Carafoli E. Eur. J. Biochem. 1992; 205: 333-340Crossref PubMed Scopus (54) Google Scholar) and may a This may be involved in specific with proteins involved in apical targeting or apical protein A differential with the first cytosolic loop of the w and x splice variants as may an to this Finally, alternative splicing at site A of PMCA2 to be In cells, a specific and from the 2w to the 2x variant This splice is on a rise in intracellular is independent of protein and be within of D.A. Strehler E.E. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). differential membrane distribution of PMCA2x and 2w variants has not been in cells, it is of that and a rise in Ca2+ are of the alternative splice at site A of PMCA2 the to PMCA2 to membrane domains where are In this be at sites in the In epithelial cells of the or the the splice may be targeted to apical in to regulation of Ca2+ alternative splicing affecting the first cytosolic loop of PMCA2 to be a for the of this Ca2+ pump to different membrane We are to and for help with the of the PMCA2b expression and to and Penniston for the PMCAs. We for and for one of how to the confocal
Chicka et al. (Thu,) studied this question.