Figure 5.

HEK-293 cells expressing the mutant Met482-Leu483del NPR-B exhibit increased baseline cGMP levels and greater cGMP responses to CNP. (A) Western blot analysis of membrane NPR-B expression levels in HEK-293 cells transfected with cDNA encoding WT or mutant NPR-B (10 μg DNA/dish). Expression was normalized to Na⁺/K⁺-ATPase expression. (B) Baseline intracellular cGMP levels (-) and effects of CNP on intracellular cGMP levels of HEK-293 cells expressing WT or mutant NPR-B. (C and D) Guanylyl cyclase activity assays with crude membranes prepared from cells expressing WT or mutant NPR-B. Membranes were incubated with vehicle (-), CNP or detergent (1% Triton X-100). cGMP production was measured by radioimmunoassay. In D, values are presented as percent of the maximal Triton-induced activity (as 100%). Means ± SEM (n = 3 independent experiments); **P < 0.01. cGMP, cyclic guanosine monophosphate; CNP, C-type natriuretic peptide; NPR, natriuretic peptide receptor.