Protein Kinase A Is a Negative Regulator of Renal Branching Morphogenesis and Modulates Inhibitory and Stimulatory Bone Morphogenetic Proteins

• Published in: The Journal of biological chemistry 1999-09, Vol.274 (37), p.26305-26314
• Main Authors: Gupta, Indra R., Piscione, Tino D., Grisaru, Silviu, Phan, Tien, Macias-Silva, Marina, Zhou, Xiaopeng, Whiteside, Catharine, Wrana, Jeffrey L., Rosenblum, Norman D.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Bone Morphogenetic Proteins - metabolism; Cyclic AMP Response Element-Binding Protein - metabolism; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic AMP-Dependent Protein Kinases - metabolism; Enzyme Activation; Kidney Tubules, Collecting - cytology; Kidney Tubules, Collecting - embryology; Mice; Morphogenesis; Recombinant Proteins - metabolism; Signal Transduction
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.37.26305

Protein kinase A (PKA) regulates morphogenetic responses to bone morphogenetic proteins (BMPs) during embryogenesis. However, the mechanisms by which PKA regulates BMP function are unknown. During kidney development, BMP-2 and high doses of BMP-7 inhibit branching morphogenesis, whereas low doses of BMP-7 are stimulatory (Piscione, T. D., Yager, T. D., Gupta, I. R., Grinfeld, B., Pei, Y., Attisano, L., Wrana, J. L., and Rosenblum, N. D. (1997) Am. J. Physiol. 273, F961–F975). We examined the interactions between PKA and these BMPs in embryonic kidney explants and in the mouse inner medullary collecting duct-3 model of collecting duct morphogenesis. H-89, an inhibitor of PKA, stimulated branching morphogenesis and enhanced the stimulatory effect of low doses of BMP-7 on tubule formation. Furthermore, H-89 rescued the inhibition of tubulogenesis by BMP-2 (or high doses of BMP-7) by attenuating BMP-2-induced collecting duct apoptosis. In contrast, 8-bromo-cAMP, an activator of PKA, inhibited tubule formation and attenuated the stimulatory effects of low doses of BMP-7. To determine mechanisms underlying the interdependence of BMP signaling and PKA activity, we examined the effect of PKA on the known signaling events in the BMP-2-dependent Smad1 signaling pathway and the effect of BMP-2 on PKA activity. PKA did not induce endogenous Smad1 phosphorylation, Smad1-Smad4 complex formation, or Smad1 nuclear translocation. In contrast, BMP-2 increased endogenous PKA activity and induced phosphorylation of the PKA effector, cAMP-response element-binding protein, in a PKA-dependent manner. We conclude that BMP-2 induces activation of PKA and that PKA regulates the effects of BMPs on collecting duct morphogenesis without activating the known signaling events in the BMP-2-dependent Smad1 signaling pathway.