The Role of Calcium Leak in Age-Dependent Loss of C. Elegans Muscle Function

Abstract

The ryanodine receptor (RyR) is a conserved, calcium release channel located in the endo/sarcoplasmic reticulum (ER/SR). RyR1 is the predominant isoform in skeletal muscle and a crucial mediator of excitation-contraction coupling. It comprises a macromolecular complex that includes the channel stabilizing protein calstabin1. Posttranslational modification of RyR1 results in calstabin1 depletion and intracellular calcium leak. In aged skeletal muscle, this leak is hypothesized to reduce the membrane potential of nearby mitochondria, which subsequently overproduce reactive oxygen species (ROS) and further oxidize RyR1, exacerbating calcium leak/muscle dysfunction. The nematode C. elegans is a well-established model with a short lifespan, ideal for aging studies; however, the underlying physiology of muscle dysfunction in C. elegans aging and the role of ROS are unknown. Therefore, we have characterized the role of calcium leak in age-dependent decline of C. elegans muscle function by examining the oxidation state of its RyR homologue, UNC-68, in WT and FKB-2 (calstabin1 homologue) KO worm strains. Our data demonstrate that UNC-68 is a macromolecular complex highly homologous to RyR1; in WT aged worms, UNC-68 is oxidized and FKB-2 is depleted from the channel. Furthermore, UNC-68 becomes oxidized earlier in the FKB-2 KO worm lifespan. FKB-2 depletion reduces peak calcium beforeand after caffeine-induced UNC-68 activation. Finally, FKB-2 KO worms have decreased motility following swimming exertion. Further studies will include ROS measurements via mitochondrial targeted, redox sensitive GFP and lifespan assays. Our goal is to demonstrate intracellular calcium leak's importance in muscle pathophysiology and establish C. elegans as a tractable model of calcium signaling mechanisms therein.