Figure 6.

NPR-A-6E displays a blunted desensitization response in whole cells. (A) Effect of ANP incubation on subsequent ANP- and detergent-dependent guanylyl cyclase activities. Human 293 cells were transiently transfected with either NPR-A (W.T.) or NPR-A-6E (6E) expression constructs. Two days later, the cells were incubated with 0.5 μM ANP for the indicated periods. The cells were then washed twice with PBS, and crude membranes were prepared and assayed for guanylyl cyclase activity in the presence of ANP, ATP, and Mg²⁺-GTP or Triton X-100 and Mn²⁺-GTP. (B) Effect of ANP incubation on the activation ratio of NPR-A-6E. The ratios of hormone-dependent over detergent-dependent guanylyl cyclase activities (ordinate) were plotted versus time of ANP incubation (abscissa). The vertical bars contained within each symbol represent the range of two separate determinations.