Signaling pathways that contribute to cell death/survival influence diseases including cancer and many neurodegenerative conditions. Elaborating signal transduction mechanisms that regulate these processes are thus important for understanding basic biology and for therapeutic intervention. Neurotrophins potently stimulate neuronal survival in part by activating the small GTP-binding protein Ras, which functions by translating neurotrophin-initiated signals into multiple signaling pathways, including PI-3 kinase/Akt and MEK/ERK, to promote survival. In the initial funding period it was proposed that a novel, and evolutionarily conserved group of Ras-related GTPases, including two mammalian proteins (Rit and Rin) and a single Drosophila ortholog (Ric), play critical roles in regulating apoptotic signaling. From this work, it is now clear that both Rit and Ric promote neuronal survival in a manner distinct from that of Ras. The original hypothesis is now expanded to address how these anti-apoptotic signaling cascades are regulated. The central hypothesis of this proposal is that the Rit GTPase functions as a molecular switch in neurons, responding to both apoptotic stresses and neurotrophin-initiated signals, to activate a distinct pro-survival signaling cascade that relies upon p38 MAP kinase signaling.
Three specific aims are proposed:
Aim 1 will characterize the ability of activated Rit to promote neuronal survival. In particular, we will assess the ability of Rit signaling to protect neurons from trophic factor-withdrawal mediated apoptosis. Using primary neurons from two transgenic mouse models either expressing activated Rit specifically in neurons or a homozygous Rit knockout mouse (developed during the previous period) it is now possible to analyze these critical issues. In addition, microarray analysis will be used to catalog the neuronal transcriptional program regulated by Rit signaling.
Aim 2 will determine the regulatory mechanism that couples NGF-stimulated TrkA to Rit activation and the nature of Rit-dependent regulation of the p38 MAP kinase cascade.
Aim 3 will explore the critical signaling pathways utilized for Rit anti-apoptotic signaling. In particular, Rit-mediated activation of both the p38- MSK1/2 kinase cascade and CREB transcriptional pathways appear to play central roles and will be tested using a combination of both cell model systems and primary neurons. Importantly, data developed since the previous review suggests that a second novel Rit-p38-HSP27-MK2 pathway may stimulate AKT signaling to afford neuronal protection. In summary, these studies will establish a role for Rit in neuronal survival. Regulation of this novel Ras-related G-protein may have a pronounced impact on neuronal physiology and would make Rit and its effectors, potential targets for the development of new therapeutic strategies.

Public Health Relevance

The death of neurons causes or contributes to various neurodegenerative disorders including stroke, epilepsy, Parkinson's disease, Huntington's disease, and Alzheimer's disease. Importantly, we have discovered a protein that promotes neuronal survival, protecting neurons from potentially lethal stimuli. Understanding the mechanism that foster neuronal survival is of fundamental importance to the development of treatment strategies for these disorders. Thus, the goal of this research is to speed progress toward therapeutic exploitation of this protein in neurodegenerative disease.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
Project #
Application #
Study Section
Neural Oxidative Metabolism and Death Study Section (NOMD)
Program Officer
Mamounas, Laura
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Kentucky
Schools of Medicine
United States
Zip Code
Mir, Sajad; Cai, Weikang; Carlson, Shaun W et al. (2017) IGF-1 mediated Neurogenesis Involves a Novel RIT1/Akt/Sox2 Cascade. Sci Rep 7:3283
Mir, Sajad; Cai, Weikang; Andres, Douglas A (2017) RIT1 GTPase Regulates Sox2 Transcriptional Activity and Hippocampal Neurogenesis. J Biol Chem 292:2054-2064
Koenighofer, M; Hung, C Y; McCauley, J L et al. (2016) Mutations in RIT1 cause Noonan syndrome - additional functional evidence and expanding the clinical phenotype. Clin Genet 89:359-66
Cai, Weikang; Andres, Douglas A (2014) mTORC2 is required for rit-mediated oxidative stress resistance. PLoS One 9:e115602
Berger, A H; Imielinski, M; Duke, F et al. (2014) Oncogenic RIT1 mutations in lung adenocarcinoma. Oncogene 33:4418-23
Cai, Weikang; Shi, Geng-Xian; Andres, Douglas A (2013) Putting the Rit in cellular resistance: Rit, p38 MAPK and oxidative stress. Commun Integr Biol 6:e22297
Cai, Weikang; Rudolph, Jennifer L; Sengoku, Tomoko et al. (2012) Rit GTPase regulates a p38 MAPK-dependent neuronal survival pathway. Neurosci Lett 531:125-30
Shi, Geng-Xian; Cai, Weikang; Andres, Douglas A (2012) Rit-mediated stress resistance involves a p38-mitogen- and stress-activated protein kinase 1 (MSK1)-dependent cAMP response element-binding protein (CREB) activation cascade. J Biol Chem 287:39859-68
Cai, Weikang; Carlson, Shaun W; Brelsfoard, Jennifer M et al. (2012) Rit GTPase signaling promotes immature hippocampal neuronal survival. J Neurosci 32:9887-97
Cai, Weikang; Rudolph, Jennifer L; Harrison, Susan M W et al. (2011) An evolutionarily conserved Rit GTPase-p38 MAPK signaling pathway mediates oxidative stress resistance. Mol Biol Cell 22:3231-41

Showing the most recent 10 out of 21 publications