Isolation and characterisation of two amylin responsive proteins from rat skeletal muscle

Abstract

Two amylin responsive proteins, here designated ARP1 and ARP2, were discovered from rat skeletal muscle through two dimensional gel electrophoresis analysis. ARP1 was detected only in amylin-stimulated muscles where the insulin-stimulated glucose incorporation into glycogen was inhibited. This protein incorporated 32Pi but not [35S]-methionine in the metabolic labeling experiments. Subsequent molecular characterisation revealed that ARP1 was a novel monomeric form (designated form 1) of protein p20, and two other monomeric forms (designated forms 2 and 3 respectively) of protein p20 were also characterised. The production of ARP1 was not affected by the presence of insulin, but calcitonin gene-related peptide (CGRP) was found to evoke the production of ARP1 in the presence or absence of insulin. In contrast, ARP2 was detected in both control and amylin-stimulated muscles. Amylin stimulation evoked incorporation of [35S]-methionine but not 32Pi into the protein and increased its concentration significantly. It is concluded that amylin elicits the production of ARP1 through phosphorylation and increases the protein biosynthesis of ARP2; the amylin-evoked production of ARP1 is insulin independent; amylin and CGRP share, at least in part, an intracellular signal transduction pathway; and ARP1 and 2 may be involved in the development of insulin resistance. It is suggested that ARP1 and 2 could potentially be used as molecular markers for the analysis of amylin action.