Positive regulator of myogenesis. Acts as cofactor for myogenic bHLH transcription factors such as MYOD1, and probably MYOG and MYF6. Enhances the DNA-binding activity of the MYOD1:TCF3 isoform E47 complex and may promote formation of a functional MYOD1:TCF3 isoform E47:MEF2A complex involved in myogenesis (By similarity). Plays a crucial and specific role in the organization of cytosolic structures in cardiomyocytes. Could play a role in mechanical stretch sensing. May be a scaffold protein that promotes the assembly of interacting proteins at Z-line structures. It is essential for calcineurin anchorage to the Z line. Required for stress-induced calcineurin-NFAT activation (By similarity). The role in regulation of cytoskeleton dynamics by association with CFL2 is reported conflictingly: Shown to enhance CFL2-mediated F-actin depolymerization dependent on the CSRP3:CFL2 molecular ratio, and also shown to reduce the ability of CLF1 and CFL2 to enhance actin depolymerization (PubMed:19752190, PubMed:24934443). Proposed to contribute to the maintenance of muscle cell integrity through an actin-based mechanism. Can directly bind to actin filaments, cross-link actin filaments into bundles without polarity selectivity and protect them from dilution- and cofilin-mediated depolymerization; the function seems to involve its self-association (PubMed:24934443). In vitro can inhibit PKC/PRKCA activity (PubMed:27353086). Proposed to be involved in cardiac stress signaling by down-regulating excessive PKC/PRKCA signaling (By similarity). May play a role in early sarcomere organization. Overexpression in myotubes negatively regulates myotube differentiation. By association with isoform 1 and thus changing the CSRP3 isoform 1:CFL2 stoichiometry is proposed to down-regulate CFL2-mediated F-actin depolymerization. Self-associates. Oligomeric in the cytoplasm and monomeric in the nucleus (By similarity). Homooligomers preferentially form along the actin cytoskeleton. Isoform 2 interacts with isoform 1 (PubMed:24934443, PubMed:24860983). Isoform 1 but not isoform 2 interacts with MYOD1 and MYOG. Isoform 1 interacts with TCAP, ACTN2 and NRAP. Isoform 2 interacts with TCAP and alpha-actinin (PubMed:24860983, PubMed:15582318, PubMed:15205937, PubMed:12507422). Interacts with LDHD. Interacts (via N-terminus)with GLRX3 (via C-terminus) and PPP3CA; GLRX3 and calcineurin compete for interaction with CSRP3. Interacts with MYF6 (By similarity). Interacts with CFL2; the stoichiometry influences F-actin depolymerization and possibly two molecules of CFL2 can interact with one molecule of CSRP3 resulting in the highest functional impact; the interaction is stronger with phosphorylated CFL2 (PubMed:19752190). Nucleocytoplasmic shuttling protein. Mainly cytoplasmic. In the Z line, found associated with GLRX3 (By similarity). Cardiac and slow-twitch skeletal muscles. Isoform 2 is expressed in striated muscle. Isoform 2 is specifically expressed at higher levels in patients with neuromuscular diseases, such as limb-girdle muscular dystrophy 2A (LGMD2A), Duchenne muscular dystrophy (DMD) and dermatomyositis (PubMed:24860983). LIM zinc-binding domain 1 is required for self-association. LIM zinc-binding domain 1 and LIM zinc-binding domain 2 both are required for optimal actin-bundling activity (PubMed:24934443). LIM zinc-binding domain 1 mediates binding to MYOD1. LIM zinc-binding domain 2 mediates binding to SPTB (By similarity). Phosphorylated by PKC/PRKCA. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry.