Myopodin

From Proteopedia

Myopodin is a protein encoded by the gene SYNPO2 [1], that is widely expressed in striated and smooth muscle cells, but seems to be differentially modified in different tissues. A protein of 80 kDa was detected in skeletal muscle, whereas the corresponding protein in the heart had a size of 95 kDa, the cause of this size difference remains to be established, but for several reasons, was suggested to be due to post translational modifications (Weins et al. 2001). In undifferentiated myoblasts, myopodin is expressed preferentially in the nucleus and only weakly in the cytoplasm. In differentiated myotubes it is incorporated into the Z-disc and shows no detectable nuclear expression. Notably, this redistribution coincides with an increase in protein expression. Together, these findings indicate that myopodin may be involved in the regulation of myocyte differentiation (Weins et al. 2001).

See The Podin Family.

Myopodin Interactions

Actin was the first binding partner of synaptopodin to be identified (Mundel et al. 1997) and is probably the most important partner. Myopodin has a novel actin binding site (Weins et al. 2001) which identification was based on the association of transiently expressed truncated myopodin fragments with stress fibres. The smallest fragment that bound to these structures contained residues 410–563 of isoform 2 of mouse myopodin [2]. Myopodin also binds to α-actinin. That interaction has been shown to involve the spectrin repeats of α-actinin (Pham and Chalovich 2006; Linnemann et al. 2010). Synaptopodin family members might be involved in the organization and anchoring of actin in the cell and might be necessary for the correct localization of α-actinin. That is supported by recent findings that during in vitro skeletal muscle cell differentiation myopodin expression precedes α-actinin expression (Linnemann et al. 2010). A newly identified filamin-binding region within the myopodin molecule, by performing yeast two-hybrid assays using carboxy-terminally and/or amino-terminally truncated constructs (Linnemann et al. 2010). The interaction was mapped to a fragment encompassing amino acids 240–521 of myopodin, i.e. a region that contains two of the previously described homology regions shared by myopodin and synaptopodin (Lin et al., 2001). The alternative transcription offers the possibility of expression of two isoforms of Myopodin, which probably differ in their binding properties for these PDZ binding domain detected, however, there is preliminary evidence that the PDZ binding domain from Myopodin interacts with Cterminal part of Synemin (Vakeel, 2006).