Subcellular localization of S100A11 (S100C, calgizzarin) in developing and adult avian skeletal muscles.

S100A11 is a member of a multigenic family of Ca(2+)-modulated proteins of the EF-hand type. We studied the subcellular localization of S100A11 in developing and adult avian skeletal muscle cells by confocal laser scanning microscopy and immunogold cytochemistry to get information about possible functional roles of this protein. Analyses of alpha-actinin, S100A1 and S100B were done in parallel for comparison. Low levels of S100A11 were found in skeletal muscle cells at embryonic day (E) 8. At E12, S100A11 was found in myotubes in the form of fine dots located between Z-discs, and on the sarcolemma and its invaginations. At E15, S100A11 was found on the sarcolemma and internal membranes, likely longitudinal tubules, where the protein was co-localized in part with S100A1 and S100B. At E18 and afterwards, co-localization of the three S100 proteins on internal membranes was almost complete. No evidence for association of S100A11 with the contractile elements of the sarcomeres was obtained. Our data suggests that, like S100A1 and S100B, S100A11 might have a role in the regulation of membrane activities, probably in relation to Ca(2+) fluxes in skeletal muscle cells.