Decreased adenylate cyclase activation by helodermin and PGE₁ in the lectin-resistant variant Wa4 of the mouse melanoma cell line B16

We examined the cultured mouse melanoma cell line B16 (clone F1) and its wheat germ agglutinin-resistant variant Wa4 that suffers from abnormal protein glycosylation (a high fucose:sialic acid ratio in glycoproteins). In both cell lines the adenylate cyclase system was endowed with a functional guanine nucleotide binding protein Gs and was efficiently coupled to α-MSH receptors. In the B16 cell line F1 studied we also observed an efficient stimulation of adenylate cyclase activity by helodermin, VIP and the VIP analogue [acetyl-His¹]VIP, and also by PGE₁. In membranes from the lectin-resistant variant Wa4, the stimulations by VIP-like peptides and by PGE₁ were reduced by 60% and 50%, respectively, while the stimulation by α-MSH remained normal. As other components of the adenylate cyclase system (Gs site, catalytical unit) appeared unchanged in the Wa4 variant, we conclude that impaired glycosylation essentially affected the number of both VIP-like peptide receptors and PGE₁ receptors.