SYNPO2

Myopodin is a 117.4 kDa protein composed of 1093 amino acids,[8] although four alternatively-spliced isoforms have been described.[9] Myopodin contains one PPXY motif, multiple PXXP motifs, and two potential nuclear localization sequences (one N-terminal and one C-terminal).[5] PPXY motifs have been shown to mediate interactions, and PXXP motifs represent potential sites of interaction for SH3 domain-containing proteins. Myopodin contains a novel actin binding site (between amino acids 410 and 563) in the center of the protein.[5]

During myotube differentiation, myopodin interacts with stress fibers prior to co-localizing with alpha actinin-2 at Z-discs in mature striated muscle cells.[5] Myopodin has been shown to shuttle between the nucleus and cytoplasm in myoblasts and myotubes in response to stress; its export from the nucleus is sensitive to lemtomycin B.[5] The nuclear localization of myopodin is sensitive to Importin 13, which directly binds myopodin and facilitates its translocation.[10] Importin binding and nuclear import of myopodin appears to be mediated by serine/threonine phosphorylation-dependent binding of myopodin to 14-3-3 beta [11] Myopodin appears to regulate compartmentalized, intracellular signal transduction between the Z-disc and nucleus in cardiac muscle cells, by forming a Z-disc signaling complex with alpha actinin-2, calcineurin, CaMKII, muscle-specific A-kinase anchoring protein, and myomegalin.[12] Specifically, phosphorylation by protein kinase A or CaMKII, and dephosphorylation by calcineurin facilitates the binding or release, respectively, of 14-3-3-beta, and the corresponding nuclear or cytoplasmic localization, respectively, of myopodin.[12]

Myopodin interacts with: