Receptor glycosylation regulates the affinity of histamine H1 receptors during smooth muscle cell differentiation.

During the cellular differentiation of the cultured smooth muscle cells, BC3H1, the Kd and the number of binding sites for [3H]-pyrilamine were decreased transiently from 276 nM to 46.5 nM and from 13.3 x 10(6)/cell to 2 x 10(6) cell, respectively. Concanavalin A (Con-A), wheat germ agglutinin, and lentil lectin inhibited [3H]pyrilamine binding to differentiated BC3H1 cells but not to undifferentiated cells. The [3H]pyrilamine binding activity of digitonin-solubilized membranes from differentiated cells was successively recovered from Con-A agarose affinity chromatography but not from undifferentiated cell membranes. The glycosylation inhibitors tunicamycin and swainsonine inhibited the expression of high affinity pyrilamine binding sites during BC3H1 cell differentiation. The molecular weight of high affinity [3H]pyrilamine binding sites on differentiated cells were approximately 68,000 as analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, which after treatment with N-glycanase was shifted to 40,000, a molecular weight similar to that of low affinity [3H]pyrilamine binding sites on undifferentiated cells. These data suggest that one element contributing to H1-receptor heterogeneity is receptor-N-glycosylation.