Protein kinase A is a negative regulator of renal branching morphogenesis and modulates inhibitory and stimulatory bone morphogenetic proteins.
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.
Gupta
I R
IR
Division of Nephrology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario.
Piscione
T D
TD
Grisaru
S
S
Phan
T
T
Macias-Silva
M
M
Zhou
X
X
Whiteside
C
C
Wrana
J L
JL
Rosenblum
N D
ND
D000818:Animals; D017209:Apoptosis; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000196:embryology*; D051379:Mice; D009024:Morphogenesis; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction
D019485:Bone Morphogenetic Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D011994:Recombinant Proteins; D017868:Cyclic AMP-Dependent Protein Kinases