Evaluation of new mechanisms in the prenylation pathway of Ras oncoproteins

• Grant number: 23/01814-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2023
• End date: December 31, 2023
• Field of knowledge: Biological Sciences - Morphology - Cytology and Cell Biology
• Principal Investigator: Enilza Maria Espreafico
• Grantee: Luana Hidemi Araki
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

RAS proteins are small GTPases that regulate a number of signaling pathways, including the mitogen-activated protein kinase (MAPK) pathway. To perform this function, RAS proteins must associate with the plasma membrane. All RAS isoforms (HRAS, NRAS and, KRAS) are post-translationally modified at a C-terminal CaaX motif to gain affinity for cell membranes. Prominent among these post-translational modifications is the farnesylation (lipidation) of RAS that occurs in the cytosol and directs RAS proteins to the cytosolic face of the endoplasmic reticulum (ER) for further processing. Previous work in our lab showed that cells silenced for EMC complex proteins, a complex of transmembrane proteins of the endoplasmic reticulum, are deficient in lipidation of the oncoprotein HRASV12, with consequent disruption of its subcellular distribution and oncogenic functions. Our laboratory postulated that the EMC complex, must play a role at two points in the RAS post-translational modification pathway: 1) pre-prenylation; 2) at one of the subsequent steps to prenylation, which involve recruitment to the endoplasmic reticulum membrane, proteolysis of the C-terminal -AAX tripeptide, methylation of the C-terminal, palmitoylation, traffic from the ER to the Golgi, and traffic to the plasma membrane. The present project will focus on elucidating the mechanisms related to the first part, i.e., how the EMC complex acts to influence the efficiency of RAS prenylation.