Regulation of protein phosphatases involved in cancer: structural studies of TIPRL and its interaction with protein phosphatase 2A

Author(s)

Valéria Scorsato

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2015-08-25

Examining board members

Ricardo Aparicio; João Renato Carvalho Muniz; Marcio Chaim Bajgelman; Celso Eduardo Benedetti; Leandro Martínez

• Advisor: Ricardo Aparicio

Abstract

The incidence of cancer in the world population continually grows year after year, reaching alarming levels. Cancer is characterized by uncontrolled cell proliferation, originated from genetic and metabolic anomalies including changes in cell signaling mediated by the reversible phosphorylation of proteins, a highly regulated process mediated by protein kinases and phosphatases. The present work focused on studies of human phosphatases PP2A and PTP1B. The protein tyrosine phosphatase PTP1B is overexpressed in tumors and is involved in cancer and other diseases such as insulin resistance and type 2 diabetes, and is considered a good target for the development of new drugs. Accordingly, we analyzed several series of small molecules for inhibitory capacity, and efforts have been made to obtain crystallographic structures of enzyme-drug complexes. PP2A is a serine-threonine phosphatase that functions as a major cellular tumor suppressor and exerts its activity as heterotrimers consisting of a catalytic subunit (PP2Ac), a scaffolding (PR65/A) and a variable regulatory subunit belonging to one of four distinct families (B/B¿/B" and striatins). The assembly process of such heterotrimers is tightly regulated by other proteins, and involves post-translational modifications at the C-terminus of PP2Ac in a process known as PP2A biogenesis. The TIPRL protein inhibits PP2A activity and there is evidence that this protein might function in the biogenesis process. This thesis reports significant advances in the study of TIPRL and its interaction with PP2Ac, such as the crystal structure of TIPRL determined from Se-Met labelled protein since there was no structural information available in databases that could be used for Molecular Replacement. The structure presents a new folding and an unexpected site binding site for the C-terminus of PP2A, which was validated by site-directed mutagenesis, pulldown and of hydrogen/deuterium exchange analysis by mass spectrometry. These results allowed us to propose a biological role for TIPRL in the biogenesis of PP2A (AU)

• FAPESP's process: 11/03054-9 - Structural characterization of the human phosphatases PTP-1B and PP2A, involved in cancer, and their interactions with inhibitors
• Grantee: Valeria Scorsato
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)