Serca Uncoupling May Facilitate Cold Acclimation in Dark-Eyed Juncos (Junco hyemalis) without Regulation by Sarcolipin or Phospholamban.

This article investigates the role of sarco/endoplasmic reticulum ATPase (SERCA) uncoupling in non-shivering thermogenesis (NST) within the pectoralis flight muscle of cold-acclimated dark-eyed juncos (Junco hyemalis). The study provides the first evidence of increased SERCA uncoupling in these birds during cold exposure (−8°C), which correlates with a reduced risk of hypothermia, suggesting a potential contribution of skeletal muscle NST to avian thermoregulation. However, this uncoupling does not appear to be mediated by the known mammalian SERCA regulatory proteins sarcolipin (SLN) or phospholamban (PLN), as SLN transcription was suppressed and PLN showed no consistent relationship with SERCA function. Additionally, SERCA uncoupling was not associated with mitochondrial biogenesis markers, indicating that the mechanisms underlying avian NST and its regulation differ from those established in mammals.