Physiological Functions Regulated by cGMP

Relaxation of smooth muscle conceivably can be achieved hy interfering with any of the steps leading to the contraction-producing phosphorylation 

In the cerebellum type I NOS and components of the cGMP signaling system are localized to a subset of cells (Schmidt et al., 1993). Purkinje cells are enriched in soluble guanylate cyclase and GKI, and neuron-specific GKI substrate protein is phosphorylated in these cells. The phosphoprotein reportedly affects neuronal signaling by inhibition of protein phosphatases 1 and 2A (Schmidt et al., 1993). 

Interconnecting NO/cGMP with Other Pathways /. cAMP 

Signaling through cAMP and NO/cGMP pathways is interconnected at the level of control of the various isoforms of cyclic nucleotide PDE. In frog ventricular myocytes Ca current 1 ) through the L-type Ca channel is regulated by cAMP-dependent kinase phosphorylation these cells also contain NO-responsive guanylate cyclase and several isoforms of cyclic nucleo- 

Arnold, W. P., Mittal, C. K., Katsuki, S., and Murad, S. (1977). Nitric oxide activates guanylate cyclase and increases guanosine 3, 5 -monophosphate levels in various tissue preparations. Proc. Natl. Acad. Sci. U.S.A. 74, 3203-3207. 

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