Journal of Biological Chemistry
Volume 275, Issue 49, 8 December 2000, Pages 38554-38560
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MEMBRANE TRANSPORT STRUCTURE FUNCTION AND BIOGENESIS
Expression of γ-Sarcoglycan in Smooth Muscle and Its Interaction with the Smooth Muscle Sarcoglycan-Sarcospan Complex*

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The sarcoglycan complex in striated muscle is a heterotetrameric unit integrally associated with sarcospan in the dystrophin-glycoprotein complex. The sarcoglycans, α, β, γ, and δ, are mutually dependent with regard to their localization at the sarcolemma, and mutations in any of the sarcoglycan genes lead to limb-girdle muscular dystrophies type 2C–2F. In smooth muscle β- and δ-sarcoglycans are associated with ε-sarcoglycan, a glycoprotein homologous to α-sarcoglycan. Here, we demonstrate that γ-sarcoglycan is also a component of the sarcoglycan complex in the smooth muscle. First, we show the presence of γ-sarcoglycan in a number of smooth muscle-containing organs, and we verify the existence of identical transcripts in skeletal and smooth muscle. The specificity of the expression of γ-sarcoglycan in smooth muscle was confirmed by analysis of smooth muscle cells in culture. Next, we provide evidence for the association of γ-sarcoglycan with the sarcoglycan-sarcospan complex by biochemical analysis and comparison among animal models for muscular dystrophy. Moreover, we find disruption of the sarcoglycan complex in the vascular smooth muscle of a patient with γ-sarcoglycanopathy. Taken together, our results prove that the sarcoglycan complex in vascular and visceral smooth muscle consists of ε-, β-, γ-, and δ-sarcoglycans and is associated with sarcospan.

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Published, JBC Papers in Press, September 18, 2000, DOI 10.1074/jbc.M007799200

*

This work was supported in part by the Muscular Dystrophy Association.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence reported in this paper has been submitted to the DDBJ/GenBankTM/EBI Data Bank with accession number AF282901.

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Supported by the Italian Telethon Grant 305/b and the Muscular Dystrophy Association.