Protein phosphorylation is of great importance in growth factor action and control of the cell cycle. Numerous protooncogenes have been identified as tyrosine or serine/threonine or serine/threonine-specific protein kinases. Growth factor receptors recruit multiple Ser/Thr protein kinases in the execution of their cellular programs. Aberrant regulation of protein kinase function is often a pivotal element in cancer pathogenesis. An understanding of the structure, regulation and role of protein kinases in cellular growth control will help in design of pharmacologic agents a specific for particular kinases which may,, in turn, serve as useful treatments for cancer. I have recently detected and purified a novel rat liver protein kinase which is likely to be an important element in growth factor signalling. The enzyme, provisionally name as pp54 MAP-2 kinase, is a 54-kDa polypeptide which avidly phosphorylates microtubule-associated protein-2. The pp54 MAP- 2 kinase coelutes with one of the major peaks of mitogen-activated MAP-2 kinase activity. Moreover, the purified pp54 MAP-2 kinase appears to have been isolated in an """"""""activated"""""""" form, in that it can be completely and specifically deactivated by treatment with the Ser/Thr phosphatase-2A, and independently by treatment with a recombinant phosphotyrosine phosphatase- 1B. The pp54 MAP-2 kinase is distinct in its substrate specificity from a p42 MAP-2 kinase described previously, however, both kinases exhibit dual regulation through Ser/Thr and Tyr-specific phosphorylation of the enzyme polypeptide, and constitute two members of a class of enzymes I have called """"""""signal-integrating"""""""" protein kinases. This application aims to study three major aspects of pp54 MAP-2 kinase. 1) Regulation: These studies will attempt to identify Ser/Thr kinases capable of reactivating the phosphatase-inactivated pp54 MAP-2 kinase. Purified Ser/Thr and Tyr-specific kinase preparations will be assayed for reactivating activity as extracts from mitogen-treated cells. 2) Substrate specificity: Preliminary evidence suggests that pp54 MAP-2 kinases favors Ser/Thr residues with prolines located immediately carboxyterminal. Proteins rich in Ser/Thr-Pro motifs, specifically, RNA polymerase-II and transcription factors which have been implicated in growth regulation, such as p53 retinoblastoma gene product and c-abl, will be assessed as substrates of pp54 MAP-2 kinase. Potential substrates will be assayed not only for phosphorylation by pp54 MAP-2 kinase but, when feasible, for changes in function which are a consequence of phosphorylation. 3) cDNA Cloning and Expression: Structural analysis of pp54 MAP-2 kinase will be useful in relating this enzyme to other known kinases. Expression studies coupled with site-directed mutagenesis will serve to elucidate the role of pp54 MAP-2 kinase in cell function and will map enzyme function and regulation to particular domains.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29GM046577-04
Application #
2184093
Study Section
Biochemistry Study Section (BIO)
Project Start
1991-08-01
Project End
1996-07-31
Budget Start
1994-08-01
Budget End
1995-07-31
Support Year
4
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02199
Georgescu, Serban P; Aronovitz, Mark J; Iovanna, Juan L et al. (2011) Decreased metalloprotease 9 induction, cardiac fibrosis, and higher autophagy after pressure overload in mice lacking the transcriptional regulator p8. Am J Physiol Cell Physiol 301:C1046-56