Calcineurin dephosphorylates the C-terminal region of filamin in an important regulatory site: a possible mechanism for filamin mobilization and cell signaling.
Filamin is a phosphoprotein that organizes actin filaments into networks. We report that a purified C-terminal recombinant region of filamin is a suitable substrate for calcineurin in vitro. Furthermore, 1 microM cyclosporin A (CsA), a specific calcineurin inhibitor, reduced the dephosphorylation of the recombinant fragment in 293FT cells. Mutagenesis analysis showed that a dephosphorylation step occurred in Ser 2152, which was previously shown to provide resistance to calpain cleavage when endogenous PKA is activated. In contrast, phosphorylation of Ser 2152 was recently reported to be necessary for membrane dynamic changes. In this regard, we found that CsA protects filamin in platelets from calpain degradation. Results could be combined with available information in a single model, assuming that some of the peptide fragments released by calcineurin-regulated calpain action could mediate actions in downstream pathways, which may help to resolve the controversies reported on the role of filamin phosphorylation in actin dynamics.
García
Elizabeth
E
Departamento de Biomedicina Molecular Cardiovascular, Instituto Nacional de Cardiología, Ignacio Chávez, Mexico DF 14080, Mexico.
Stracher
Alfred
A
Jay
David
D
D000199:Actins / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002154:Calpain / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003285:Contractile Proteins / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D064448:Filamins; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D016296:Mutagenesis; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction
D000199:Actins; D065095:Calcineurin Inhibitors; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; D011994:Recombinant Proteins; D012694:Serine; D016572:Cyclosporine; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D002154:Calpain