Mitogen activated protein kinases (MAPKs) are key signaling enzymes that are activated by phosphorylation of a TXY motif in their activation loops. While dual-specificity MAPK kinases activate many MAPKs (canonical signaling), atypical kinases and autophosphorylation can also activate MAPKs (non-canonical signaling). A great deal is known about the role of canonical signaling pathways in health and disease. Much less is known about non-canonical signaling. Smk1 is a meiosis- specific MAPK in the yeast S. cerevisiae that controls gamete formation (sporulation) through a non-canonical signaling pathway that generates different forms of the MAPK at different stages of meiosis. First, the CDK activating kinase, Cak1, phosphorylates Smk1's activating T-residue as the meiotic divisions are taking place. This monophosphorylated form of Smk1 is distributed throughout the cell. Later in the program (at anaphase II), a meiosis-specific protein, Ssp2, binds to Smk1 and activates the cis-autophosphorylation of its Y-residue. This reaction occurs at specific membraneous structures that cellularize the haploids generated in this specialized cell division. Thus, Ssp2 delivers a pulse of the doubly phosphorylated MAPK to the ?right place? at the ?right time? in this developmental program. This spatiotemporal specificity is achieved by modularity of the Ssp2 protein; it is localized by a targeting domain (TD) and it activates cis-autophosphorylation of the MAPK via a kinase activating domain (KAD). The Ssp2KAD is itself composed of segments that bind Smk1 and a regulatory RNA recognition motif (RRM). This proposal is to use the Ssp2KAD/Smk1 reaction as a model to study autoactivation of MAPKs in the context of a developmental system.
The specific aims of this proposal are: 1- Elucidate molecular mechanisms of non-canonical MAPK signaling using a bacterial reconstitution system and purified proteins, 2-Test a competition-based switch-site model for Smk1 activation, and 3- Identify the RNA(s) recognized by the RNA recognition motif in Ssp2.

Public Health Relevance

Mitogen activated protein kinases (MAPKs) are key regulators of cell growth, differentiation, and apoptosis, that are dysregulated in a variety of diseases/disorders ranging from birth defects to cancer, to Alzheimer's disease. This project will use yeast as a model system to study MAPK autoactivation, a poorly understood regulatory mechanism that activates MAPKs, and MAPK-like kinases. The proposed studies will generate new insights into mechanisms that control MAPK signaling that impact health and disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM120090-01
Application #
9156321
Study Section
Cellular Signaling and Regulatory Systems Study Section (CSRS)
Program Officer
Maas, Stefan
Project Start
2016-08-15
Project End
2020-05-31
Budget Start
2016-08-15
Budget End
2017-05-31
Support Year
1
Fiscal Year
2016
Total Cost
$309,312
Indirect Cost
$109,312
Name
Thomas Jefferson University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
053284659
City
Philadelphia
State
PA
Country
United States
Zip Code
19107
Omerza, Gregory; Tio, Chong Wai; Philips, Timothy et al. (2018) The meiosis-specific Cdc20 family-member Ama1 promotes binding of the Ssp2 activator to the Smk1 MAP kinase. Mol Biol Cell 29:66-74
Tio, Chong Wai; Omerza, Gregory; Phillips, Timothy et al. (2017) Ssp2 Binding Activates the Smk1 Mitogen-Activated Protein Kinase. Mol Cell Biol 37: