Regulation
of Adenylyl Cyclase
The enzyme adenylyl cyclase synthesizes the intracellular second messenger cyclic AMP, which plays a key role in functions ranging from control of heart rate and force of contraction to learning and memory. Our laboratory is using structural, biochemical, and molecular biology techniques to understand the complex regulation of adenylyl cyclase by heterotrimeric GTP-binding proteins. We are currently pursuing the structural and kinetic mechanism of inhibition of cardiac adenylyl cyclase by the inhibitory G protein subunit, Gi alpha. In addition we are examining how localization of adenylyl cyclase to specific complexes plays a role in cellular signaling.
Another potential regulator of adenylyl cyclase signaling pathways is the family of proteins known as regulators of G protein signaling (RGS). We have discovered that members of this protein family can greatly influence adenylyl cyclase activity. This may represent a novel mechanism for the down regulation of cyclic AMP accumulation in cardiac cells, an important element in the progression of heart disease. We are using recombinant adenoviral technology in combination with biochemical and cellular techniques to probe the role of RGS proteins in adenylyl cyclase regulation.
Our lab is also interested in the signaling mechanism of the polypeptide hormone relaxin and its ability to increase cyclic AMP by activation of the G protein coupled receptor (LGR7/8) and phosphoinositide 3-kinase (PI3K). Relaxin stimulates adenylyl cyclase activity by two distinct pathways that are temporally separable, both as a consequence of LGR7/8 stimulation. These include direct activation by Gs alpha and indirect activation via PI3K. Current studies are using immunofluorescence, antisense oligonucleotides, and pharmacological inhibitors to further probe this signaling pathway in a number of pathological systems.
The structure of the cytoplasmic domains of adenylyl cyclase bound to forskolin
is shown (C1 domain
in gold; C2 domain in purple). The movement of these domains
upon binding substrate is highlighted in a and b. Those regions that
undergo the most movement are colored in red. Regulators of the enzyme
will ultimately control the dynamics of these domains.
Dessauer, C.W. and Nguyen, B.T. (2005) Relaxin Stimulates Multiple Signaling Pathways: Activation of cAMP, PI3K, and PKCz in THP-1 cells. Annals of N.Y. Acad. Sciences, 1041: 272-279.
Nguyen, B.T. and Dessauer, C.W. (2005) Relaxin Stimulates PKCz Translocation via PI3K to Increase cAMP Production in THP-1 Cells. Mol. Endo., 19: 1012-1023.
Chen-Goodspeed, M., Lukan, A.N., and Dessauer, C.W. (2005) Modeling of Gai and Gas Regulation by Human Types V and VI Adenylyl Cyclase. J. Biol. Chem., 280: 1808-1816.
Salim, S. and Dessauer, C.W. (2004) Analysis of the Interaction between RGS2 and Adenylyl Cyclase. Methods in Enzymology 390: 83-99.
Salim, S., Sinnarajah, S., Kehrl, J.H., and Dessauer, C.W. (2003) Identification of RGS2 and Type V Adenylyl Cyclase Interaction Sites. J. Biol. Chem. 278: 15842 - 15849
Nguyen, B.T., Yang, L., Sanborn, B.M., and Dessauer, C.W. (2003) Phosphoinositide 3-Kinase Activity is Required for Biphasic Stimulation of cyclic AMP by Relaxin. Mol. Endocrinol. 17(6): 1075-84.
Dessauer, C.W., Chen-Goodspeed, M., and Chen, J. (2002) Mechanism of Gia-Mediated Inhibition of Type V Adenylyl Cyclase. J. Biol. Chem. 277: 28823-28829.
Sinnarajah, S., Dessauer, C.W., Srikumar, D., Chen, J., Yuen, J., Yilman, S., Dennis, J.C. Morrison, E.E., Vodyanoy, V., and Kehrl, J.H. (2001) RGS2 Regulates Signal Transduction in Olfactory Neurons by Attenuating Adenylyl Cyclase III Activation. Nature 409: 1051-1055.
