ound that Sspn migrated in the denser gradient fractions, along with the β-, δ-, and ϵ-SG and β-DG. The tight association of these proteins upon solubilization indicates that these proteins are integral components of a multisubunit complex that via DG can function as a novel ECM receptor in the white adipocytes. Control experiments in differentiated 3T3-L1 cells supported this conclusion as well (data not shown).

To determine whether the adipose SG complex functions as a single unit, we tested whether the loss of a single component will influence the expression of the others and impair α-DG function. We took advantage of existing mouse models of muscular dystrophy, each with a systemic genetic ablation of one skeletal DGC component ([@B32]). [Fig. 2](#F2){ref-type="fig"}*A* shows the composition of the SG complex and its associated Sspn and DG in mdx and mdx3cv mice, utrophin (utrn), β-SG, δ-SG, and α-SG null mice. As expected, loss of either full-length dystrophin (dys) or α-SG, whose expression are restricted to skeletal muscle, had no consequence on the expression of the SGs, Sspn, and DG at the adipocyte membrane nor on the ability of α-DG to bind laminin. The loss of all dys isoforms in mdx3cv mice or of utrn in the utrn null mice was accompanied by modest decreased expression of all the proteins tested and a reduced laminin binding to α-DG. Therefore, although one cannot rule out that a short dys isoform and utrophin could be expressed in the adipocytes, their expression does not appear to be critical for proper SG complex expression at the adipocyte plasma membrane. However, loss of either β-SG or δ-SG led to a complete loss of the other SGs as well as Sspn. Moreover, only residual expression of the glycosylated form of α-DG could be detected, which correlated with weak residual laminin binding. Altogether, our data suggest that the adipose SG complex should be considered as a single unit that relies on all its individual components for full functionality.

![**β-SG null mice are glucose-in