Skeletal muscle alpha actin (ACTA1) acetylation negatively regulates muscle function in response to obesity

Abstract

Post‐translational modifications (PTMs) of proteins are an increasingly important area of study that contributes to our understanding for protein function in the control of health and disease. Acetylation, for example, has long been associated with histone modifications to control gene expression, yet emerging omics data demonstrates that acetylation occurs across the proteome. Our most recent work further shows global shifts in non‐histone protein acetylation within the left ventricle (LV) in response to diet‐induced obesity. Despite these advances in omics technologies, our understanding for how non‐histone protein acetylation regulates cardiac biology remains a ‘black box’. In this study, we examined the functional importance for skeletal muscle alpha actin (ACTA1) acetylation in the control of muscle function. For this, we used actin‐motility assays to examine the biophysical changes between acetylated ACTA1 and the other myofibrillar proteins involved in cardiac contraction and relaxation (e.g. myosin, tropomyosin). Here, we show that ACTA1 acetylation increased actin‐myosin binding, decreased actin sliding velocity and increased Ca2+ sensitivity. These data suggest that ACTA1 acetylation significantly alters muscle function. Of note, we previously published that lysine (K) residue 50 (K50) of ACTA1 was acetylated, similar to other proteomics reports. Interestingly, the positively charged K50 on ACTA1 sits juxtaposed to the negatively charged aspartic acid (D) residue 391 of the cardiac myosin binding protein (cMy‐BP). cMy‐BP is essential for actin‐myosin interactions, and this suggests an important role for ACTA1 K50 acetylation in the control of muscle contraction. Thus, we knocked out endogenous actin (Act88F) from the indirect flight muscles (IFMs) of D. melanogaster and inserted an Act88F K50Q mutant, which mimics acetylation specifically at this site. Previous reports have shown that IFMs behave similarly to cardiac muscle. Phenotypically, the K50Q flies behave similar to their wild‐type counterparts. However, current studies are underway to examine changes in flight as well as purify the K50Q actin for actin‐motility assays to examine biophysical changes in myofibrillar proteins. Combined, our data suggests that ACTA1 acetylation negatively impacts muscle function in response to obesity, current work will determine the implications for K50 actin acetylation in this phenotype.