Proteoglycan biosynthesis is required in BC3H1 myogenic cells for modulation of vascular smooth muscle α‐actin gene expression in response to microenvironmental signals

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Abstract
Induction of vascular smooth muscle (VSM) α‐actin mRNA expression during cytodifferentiation of mouse BC3H1 myogenic cells coincides with the accumulation of cell surface‐ and extracellular matrix‐associated sulfated proteoglycans. Inhibition of proteoglycan biosynthesis in myogenic cells using an artificial b̃‐D‐xyloside glycosaminoglycan acceptor was accompained by a reduction in cell surface/extracellular matrix proteoglycans and VSM α‐actin mRNA expression while enhanciang the secretion of free chondroitin sulfate/dermatan sulfate and heparan sulfate glycosaminoglycans into the culture medium. Maximum inhibition of VSM α‐actin mRNA expression required that proteoglycan biosynthesis be blocked during the early phase of cytodifferentiation when myoblasts were fully confluent and quiescent. The inhibitory effect of b̃‐D‐xyloside on α‐actin mRNA expression resulted from attenuation at both the transcriptional and post‐transcriptional control points. Sustained proteoglycan biosynthesis was required for induction of VSM α‐actin mRNA in quiescent myoblasts in response to cytodifferentiation‐permissive, substrate‐associated macromolecules (SAM) or upon exposure to soluble serum factors capable of transiently stimulating VSM α‐actin gene transcription. The results suggested that efficient myoblast cytodifferentiation and modulation of VSM α‐actin mRNA levels depended on intact cell surface proteoglycans to convey signals generated as a consequence of cellular interaction with substrate components and serum factors.

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