α7ß1 Integrin regulation of gene transcription in skeletal muscle following an acute bout of eccentric exercise.

The α7ß1 integrin is concentrated at the costameres of skeletal muscle and provides a critical link between the actin cytoskeleton and laminin in the basement membrane. We previously demonstrated that expression of the α7BX2 integrin subunit (MCK:α7BX2) preserves muscle integrity and enhances myofiber cross-sectional area following eccentric exercise. The purpose of this study was to utilize gene expression profiling to reveal potential mechanisms by which the α7BX2-integrin contributes to improvements in muscle growth after exercise. A microarray analysis was performed using RNA extracted from skeletal muscle of wild-type or transgenic mice under sedentary conditions and 3 h following an acute bout of downhill running. Genes with false discovery rate probability values below the cutoff of P < 0.05 (n = 73) were found to be regulated by either exercise or transgene expression. KEGG pathway analysis detected upregulation of genes involved in endoplasmic reticulum protein processing with integrin overexpression. Targeted analyses verified increased transcription of Rpl13a, Nosip, Ang, Scl7a5, Gys1, Ndrg2, Hspa5, and Hsp40 as a result of integrin overexpression alone or in combination with exercise (P < 0.05). A significant increase in HSPA5 protein and a decrease in CAAT-enhancer-binding protein homologous protein (CHOP) were detected in transgenic muscle (P < 0.05). In vitro knockdown experiments verified integrin-mediated regulation of Scl7a5 The results from this study suggest that the α7ß1 integrin initiates transcription of genes that allow for protection from stress, including activation of a beneficial unfolded protein response and modulation of protein synthesis, both which may contribute to positive adaptations in skeletal muscle as a result of engagement in eccentric exercise.