Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, C80
HMG-CoA reductase role in rat skeletal myoblast differentiation
L. Trapani1, C. Martini1, M. Marino1, V. Pallottini1
1. University Roma Tre, Rome, Italy.
3-hydroxy 3-methylglutaryl Coenzyme A reductase (HMG-CoAR) is the key and rate limiting enzyme of cholesterol biosynthetic pathway (Goldstein and Brown, 1990). Besides cholesterol, HMG-CoAR end-products such as farnesyl-pyrophosphate (FPP) and geranyl pyrophosphate (GGPP) are essential compounds for survival, proliferation and differentiation of cells (Ogura et al., 2007) through the activation of small GTPases, such as Ras and RhoA (Allal et al., 2000; Prendergast and Oliff, 2000). Although HMG-CoAR activity has already been related to the differentiation of some cellular lines there are no studies that analyse the role of HMG-CoAR, and the pathway it is involved with, in a fully characterized muscle differentiation model. Thus, the aim of this work is to evaluate such role and delineate the pathway involved in foetal rat myoblasts (L6) induced to differentiate by insulin, a standard and feasible model of the myogenesis, a dynamic process characterised by the proliferation, the withdrawal from the cell cycle and the fusion of mononucleated undifferentiated myoblasts into myotube. The aim is supported by experimental and clinical studies that demonstrate how HMG-CoAR strong inhibiting statins, widely used in therapies against hypercholesterolemia, could cause myopathy characterized by weakness, pain, and elevated serum creatine phosphokinase (Christopher-Stine 2006), thus demonstrating the important role of HMG-CoAR in muscular physiology. To this end the differentiation was monitored both by biochemical and morphological approaches; protein levels were analysed through western blotting assays; cholesterol and prenylated protein cellular content have been analysed through TLC and radioisotopic assay respectively. The results obtained by biochemical and morphological approaches demonstrate that (i) HMG-CoAR increase is crucial for differentiation induction, (ii) p21waf, whose increase is a necessary requisite for differentiation to occur, rises downstream HMG-CoAR activation, (iii) p38/MAPK pathway, key regulator of differentiating process, has a main role also for HMG-CoAR activation durind the early phase of L6 differentiation. Pathologies characterized by muscle degeneration might benefit from therapeutic programmes committed to muscle function restoration, such as modulation and planning myoblast differentiation. Thus, the important role of HMG-CoAR in muscular differentiation providing new molecular basis for the control of muscle development could be helpful in the design of therapeutic treatment committed to potentiation of regenerative ability of muscle tissue in degenerative myopathies and in diseases characterised by the weakening of muscular fibres and aging-related disorders (sarcopenia).
Where applicable, experiments conform with Society ethical requirements