Proteolytic activation of membrane-bound guanylate cyclase

Membrane-bound guanylate cyclase-A (GC-A), the receptor for atrial natriure tic factor (ANF), has been shown to be regulated by its kinase-like domain. To resolve the nature of this regulation, we measured the effects of vario us proteases on the activity of guanylate cyclase in rat lung membranes, an d on the activity of the bacterial-expressed catalytic domain (GC-c) and on a recombinant peptide composed of both the kinase-like and catalytic domai n (GC-kc) of guanylate cyclase. Pronase increased rat guanylate cyclase act ivity in a biphasic manner with a maximal effect at about 10-20 mug per ass ay tube. Thermolysin had effects similar to those of pronase on the activit y of guanylate cyclase in rat lung membranes. In the case of bacterial-expr essed proteins, pronase increased the activity of GC-kc, but not GC-c. Thes e results indicate that GC-A contains an autoinhibitory site on its kinase- like domain, and that removal of the autoinhibitory site by limited proteol ysis leads to enzyme activation. GC-A was poorly activated by ANF and ATP a fter the rat lung membrane was pretreated with pronase, suggesting that ANF /ATP and pronase activate guanylate cyclase through the same mechanism. It is suggested that the binding of ANF and ATP to GC-A may induce a conformat ional change of the receptor that releases the inhibitory constraint on enz yme activity leading to enzyme activation. (C) 2001 Elsevier Science Inc. A ll rights reserved.