Heterozygous SOD2 deletion selectively impairs SERCA function in the soleus of female mice

Abstract

The sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) restores intracellular Ca2+ ([Ca2+]i) to resting levels after muscle contraction, ultimately eliciting relaxation. SERCA pumps are highly susceptible to tyrosine (T)‐nitration, impairing their ability to take up Ca2+ resulting in reduced muscle function and increased [Ca2+]i and cellular damage. The mitochondrial antioxidant enzyme, superoxide dismutase 2 (SOD2), converts superoxide radicals into less reactive H2O2. Heterozygous deletion of SOD2 (Sod2+/−) in mice increases mitochondrial oxidative stress; however, the consequences of reduced SOD2 expression in skeletal and cardiac muscle, specifically the effect on SERCA pumps, has yet to be investigated. We obtained soleus, extensor digitorum longus (EDL), and left ventricle (LV) muscles from 6 to 7 month‐old wild‐type (WT) and Sod2+/− female C57BL/6J mice. Ca2+‐dependent SERCA activity assays were performed to assess SERCA function. Western blotting was conducted to examine the protein content of SERCA, phospholamban, and sarcolipin; and immunoprecipitation experiments were done to assess SERCA2a‐ and SERCA1a‐specific T‐nitration. Heterozygous SOD2 deletion did not alter SERCA1a or SERCA2a expression in the soleus or LV but reduced SERCA2a in the EDL compared with WT, though this was not statistically significant. Soleus muscles from Sod2+/− mice showed a significant reduction in SERCA’s apparent affinity for Ca2+ when compared to WT, corresponding with significantly elevated SERCA2a T‐nitration in the soleus. No effect was seen in the EDL or the LV. This is the first study to investigate the effects of SOD2 deficiency on muscle SERCA function and shows that it selectively impairs SERCA function in the soleus.

Loss of neuronatin increases susceptibility of SERCA to thermal inactivation

“…We then examined maximal SERCA activity in the soleus homogenates using an enzyme-linked spectrophotometric assay [14, 15] at a p Ca of 5.0. In a basal state, there were no differences in SERCA V max between WT and NNAT KO mice (Figure 1B).…”

Transcriptomic and Phenotypic Analysis of CRISPR/Cas9-Mediated gluk2 Knockout in Zebrafish

“…At the same time, GluK2 sensing cold is a dynamin-dependent process regulated by releasing the peak Ca 2+ transient [ 16 ]. Inevitably, the impairment of taking up Ca 2+ would do great damage to muscle and cellular function [ 34 ].…”

A Novel Imaging Method (FIM-ID) Reveals that Myofibrillogenesis Plays a Major Role in the Mechanically Induced Growth of Skeletal Muscle

“…To accomplish this, we took advantage of the fact that myofibrils are largely surrounded by a sarcoplasmic reticulum (SR) that is highly enriched with an enzyme called the sarco(endo)plasmic reticulum calcium-ATPase (SERCA) [30][31][32]. There are two major isoforms of SERCA (SERCA1 which is found in Type II fibers, and SERCA2 which is found in Type I fibers), and monoclonal antibodies for each isoform have been in existence for many years [32][33][34][35][36]. Importantly, these antibodies have been shown to possess excellent reactivity in both flash-frozen and aldehyde-fixed tissues [37][38][39].…”