The sarcoplasmic/endoplasmic reticulum calcium ATPase 1 (SERCA1) has two muscle specific splice isoforms; SERCA1a in fast-type adult and SERCA1b in neonatal and regenerating skeletal muscles. At the protein level the only difference between these two isoforms is that SERCA1a has C-terminal glycine while SERCA1b has an octapeptide tail instead. This makes the generation of a SERCA1a specific antibody not feasible. The switch between the two isoforms is a hallmark of differentiation so we describe here a method based on the signal ratios of the SERCA1b specific and pan SERCA1 antibodies to estimate the SERCA1b/SERCA1a dominance on immunoblot of human muscles. Using this method we showed that unlike in mouse and rat, SERCA1b was only expressed in pre-matured infant leg and arm muscles; it was replaced by SERCA1a in more matured neonatal muscles and was completely absent in human foetal and neonatal diaphragms. Interestingly, only SERCA1a and no SERCA1b were detected in muscles of 7–12 years old boys with Duchenne, a degenerative-regenerative muscular dystrophy. However, in adult patients with myotonic dystrophy type 2 (DM2), the SERCA1b dominated over SERCA1a. Thus the human SERCA1b has a different expression pattern from that of rodents and it is associated with DM2.
ASJC Scopus subject areas
- Cell Biology