title: Role of Ca2+ in proteolysis-inducing factor (PIF)-induced atrophy of skeletal muscle.
abstract: Proteolysis-inducing factor (PIF) induces muscle loss in cancer cachexia through a high affinity membrane bound receptor. This study investigates the mechanism by which the PIF receptor communicates to intracellular signalling pathways. C(2)C(12) murine myoblasts were used as a model using PIF purified from MAC16 tumours. Calcium imaging was determined using fura-4-acetoxymethyl ester (Fura-4-AM). PIF induced a rapid rise in Ca(2+)(i), which was completely attenuated by a anti-receptor antibody, or peptides representing 20 mers of the N-terminus of the PIF receptor. Other agents catabolic for skeletal muscle including angiotensin II (AngII) tumour necrosis factor-α (TNF-α) and lipopolysaccharide (LPS) also induced a rise in Ca(2+)(i), but this was not attenuated by anti-PIF-receptor antibody. The rise in Ca(2+)(i) induced by PIF and AngII was completely attenuated by the Zn(2+) chelator D-myo-inositol-1,2,6-triphosphate, and this was reversed by administration of exogenous Zn(2+). The Ca(2+)(i) rise induced by PIF was independent of the presence of extracellular Ca(2+), and attenuated by the Ca(2+) pump inhibitor thapsigargin, suggesting that the Ca(2+)(i) rise was due to release from intracellular stores. This rise in Ca(2+)(i) induced by PIF was attenuated by both the phospholipase C inhibitor U73122 and 2-APB, an inhibitor of the inositol 1,4,5-triphosphate receptor, suggesting the involvement of a G-protein. Binding of the PIF to its receptor in skeletal muscle triggers a rise in Ca(2+)(i), which initiates a signalling cascade leading to a depression in protein synthesis, and an increase in protein degradation.
authors: Nutritional Biomedicine, School of Life and Health Sciences, Aston University, Birmingham, UK. k.a.mirza@aston.ac.uk
authors: K A
authors: KA
authors: Mirza
authors: M J
authors: MJ
authors: Tisdale
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001284:Atrophy / Q000378:metabolism; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011509:Proteoglycans / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D001896:Boron Compounds; D002614:Chelating Agents; D004963:Estrenes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008070:Lipopolysaccharides; D011509:Proteoglycans; D011760:Pyrrolidinones; D014409:Tumor Necrosis Factor-alpha; C042057:proteolysis-inducing peptide; D000804:Angiotensin II; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C109986:2-aminoethoxydiphenyl borate; D010738:Type C Phospholipases; D015032:Zinc; D002118:Calcium