title: Regulation of GAP43/calmodulin complex formation via calcineurin-dependent mechanism in differentiated PC12 cells with altered PMCA isoforms composition.
abstract: Several lines of evidence suggest the contribution of age-related decline in plasma membrane calcium pump (PMCA) to the onset of neurodegenerative diseases. From four PMCA isoforms, PMCA2, and PMCA3 respond to a rapid removal of Ca(2+) and are expressed predominantly in excitable cells. We have previously shown that suppression of neuron-specific PMCAs in differentiated PC12 cells accelerated cell differentiation, but increased apoptosis in PMCA2-deficient line. We also demonstrated that altered expression of voltage-dependent calcium channels correlated with their higher contribution to Ca(2+) influx, which varied between PMCA-reduced lines. Here, we propose a mechanism unique for differentiated PC12 cells by which PMCA2 and PMCA3 regulate pGAP43/GAP43 ratio and the interaction between GAP43 and calmodulin (CaM). Although down-regulation of PMCA2 or PMCA3 altered the content of GAP43/pGAP43, of paramount importance for the regulatory mechanism is a disruption of isoform-specific inhibitory PMCA/calcineurin interaction. In result, higher endogenous calcineurin (CaN) activity leads to hypophosphorylation of GAP43 in PMCA2- or PMCA3-deficient lines and intensification of GAP43/CaM complex formation, thus potentially limiting the availability of free CaM. In overall, our results indicate that both "fast" PMCA isoforms could actively regulate the local CaN function and CaN-downstream processes. In connection with our previous observations, we also suggest a negative feedback of cooperative action of CaM, GAP43, and CaN on P/Q and L-type channels activity. PMCAs- and CaN-dependent mechanism presented here, may signify a protective action against calcium overload in neuronal cells during aging, as well a potential way for decreasing neuronal cells vulnerability to neurodegenerative insults.
authors.affiliation: Department of Molecular Neurochemistry, Medical University of Lodz, 6/8 Mazowiecka Str., 92-215, Lodz, Poland, tomasz.boczek@umed.lodz.pl.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Boczek
authors.forename: Bozena
authors.initials: B
authors.lastname: Ferenc
authors.forename: Malwina
authors.initials: M
authors.lastname: Lisek
authors.forename: Ludmila
authors.initials: L
authors.lastname: Zylinska
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D019922:GAP-43 Protein / Q000378:metabolism*; D005786:Gene Expression Regulation; D010766:Phosphorylation; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction
chemical_list: C506961:Atp2b2 protein, rat; C000598609:Atp2b3 protein, rat; D002147:Calmodulin; D019922:GAP-43 Protein; D020033:Protein Isoforms; D019703:Calcineurin; D053499:Plasma Membrane Calcium-Transporting ATPases