Intra-mitochondrial location of the skeletal muscle perilipin 3 and 5 proteins at rest and following electrically stimulated contraction

Abstract

PLIN3 and PLIN5 have been shown to localize to skeletal muscle mitochondria. Hypotheses state that these PLINs could facilitate lipid droplet-mitochondrial interactions, however, this would presumably require that they would localize to the outer mitochondrial membrane (OMM). The purpose of this study was to sub-fractionate skeletal muscle mitochondria at rest and following contraction to determine the precise intra-mitochondrial localization of PLIN3 and PLIN5. At rest, PLIN5 was primarily found in the OMM/intermembrane space (IMS) fraction, however, following contraction there was a redistribution of PLIN5 protein content towards the mitoplasts. PLIN3 protein content localized to the OMM/IMS at rest and was unchanged with stimulation. Co-immunoprecipitation found PLIN5 associated with both ACSL1 and CPT I at rest and following contraction while PLIN3 only associated with ACSL1. CPT I and II also associate, allowing for a link between the two membranes that may help explain the shift of PLIN5 to the mitoplast following contraction.