Silencing SERCA1b in a few fibers stimulates growth in the entire regenerating soleus muscle

Abstract

The neonatal isoform of the sarcoplasmic/endoplasmic reticulum Ca²(+) ATPase 1 (SERCA1b) is a dominant Ca²(+) pump in the young fibers of regenerating muscle. In vivo transfection of about 1% of the fibers with SERCA1b RNAi plasmid resulted in no apparent change in the transfected fibers, but enhanced the increase of fresh weight and fiber size in the whole regenerating rat soleus muscle, until the normal size was reached. Co-transfection of calcineurin inhibitor cain/cabin-1 with SERCA1b RNAi was sufficient to cut down the widespread growth stimulation, but the subsequent transfection of cain into the SERCA1b RNAi transfected muscle did not inhibit muscle growth. The SERCA1b RNAi preferably upregulated the expression of the NFAT reporter lacZ compared to controls when co-transfected into the fibers. Notably, perimuscular injection of interleukin-4 (IL-4) antibody but not that of an unrelevant antibody completely abolished the growth-promoting effect of SERCA1b RNAi. This indicates that silencing SERCA1b in a few fibers stimulates the calcineurin-NFAT-IL-4 pathway and fiber growth in the whole regenerating soleus. These results suggest the presence of an autocrine-paracrine coordination of growing muscle fibers, and put forward a new method to stimulate skeletal muscle regeneration.

The Effect of SERCA1b Silencing on the Differentiation and Calcium Homeostasis of C2C12 Skeletal Muscle Cells

“…SERCA1b was successfully silenced in 75% of stably transfected clones. The results presented here are complementary to the SERCA1b silencing in regenerating muscle [ 15 ] and show for the first time the importance of the neonatal calcium pump in calcium handling, proliferation, and myotube development of myogenic cells.…”

“…The function of SERCA1b has partially been uncovered by injecting regenerating m . soleus of the rat with a plasmid expressing an shRNA targeted against its mRNA [ 15 ]. Although less than 1% of the fibers and even less than 0.1% of the myonuclei were successfully transfected [ 16 ] it remarkably stimulated growth also in the non-transfected fibers and in the entire regenerating muscle.…”

P-type ATPases at a glance

“…SERCA1, for example, is expressed as the 1a isoform in the adult fast-twitch muscle and as the 1b isoform -with an extended Cterminus -exclusively in fetal and regenerating tissue (Zador et al, 2011). SERCA2a is mainly found in cardiac and slow-twitch muscle, whereas SERCA2b is ubiquitously expressed (Wuytack et al, 2002).…”

Recent progress in histochemistry and cell biology

“…-pump controls the development of muscle fibers, but not that of mature fibers (Zador et al 2007). Zador et al (2011) thus could demonstrate that gene therapy of regenerating skeletal muscles might be possible with only a few fibers transfected.…”

“…dependency as the corresponding adult fast type muscle SERCA1a isoform (Maruyama and MacLennan 1988). Since there is no apparent difference between these two isoforms Zador et al (2011) set out to investigate the role of SERCA1b in young fibers of regenerating soleus muscle in rat, where it is specifically expressed. RNAi was used to silence SERCA1a in vivo.…”