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 (PubMed:9039266, PubMed:15665106). The role in regulation of cytoskeleton dynamics by association with CFL2 is reported conflictingly. 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 (By similarity). In vitro can inhibit PKC/PRKCA activity. Proposed to be involved in cardiac stress signaling by down-regulating excessive PKC/PRKCA signaling (PubMed:27353086). Self-associates. Oligomeric in the cytoplasm and monomeric in the nucleus. Homooligomers preferentially form along the actin cytoskeleton (By similarity). Interacts with TCAP (PubMed:20044516). Interacts with LDHD, MYOD1, MYOG, ACTN2, NRAP, MYF6 (By similarity). Interacts (via N-terminus)D with GLRX3 (via C-terminus) and PPP3CA; GLRX3 and calcineurin compete for interaction with CSRP3 (PubMed:18258855). 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 (By similarity). Nucleocytoplasmic shuttling protein (By similarity). Mainly cytoplasmic. In the Z line, found associated with GLRX3 (via C-terminus). 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. LIM zinc-binding domain 1 mediates binding to MYOD1. LIM zinc-binding domain 2 mediates binding to SPTB. Phosphorylated by PKC/PRKCA. Mutant mice developed dilated cardiomyopathy with hypertrophy and heart failure after birth. Ultrastructural analysis revealed a dramatic disruption of cardiomyocyte cytoarchitecture. At birth, these hearts are not hypertrophic, but already abnormally soft, with cell-autonomous and Csrp3-sensitive alterations in cytoarchitecture. The morphological, functional, and molecular features of the cardiac phenotype in mutant adult mice are undistinguishable from those seen in human heart failure resulting from dilated cardiomyopathy of various etiolologies, these mice can thus be used as model. Heterozygous mice display a more pronounced left ventricular dilation and systolic dysfunction and decreased survival after myocardial infarction.