Journal Article

Transamidase site-targeted agents alter the conformation of the transglutaminase cancer stem cell survival protein to reduce GTP binding activity and cancer stem cell survival

Eckert, R L, Keillor, J W, Kerr, C, Lakowicz, J R, Lok Wong, T, Weber, D J, Szmacinski, H, Fisher, M L, Akbar, A, Godoy-Ruiz, R, Toth, E A, Nance, B

2017

Overview

Type 2 transglutaminase (TG2) is an important cancer stem cell survival protein that exists in open and closed conformations. The major intracellular form is the closed conformation that functions as a GTP-binding GTPase and is required for cancer stem cell survival. However, at a finite rate, TG2 transitions to an open conformation that exposes the transamidase catalytic site involved in protein–protein crosslinking. The activities are mutually exclusive, as the closed conformation has GTP binding/GTPase activity, and the open conformation transamidase activity. We recently showed that GTP binding, but not transamidase activity, is required for TG2-dependent cancer stem cell invasion, migration and tumour formation. However, we were surprised that transamidase site-specific inhibitors reduce cancer stem cell survival. We now show that compounds NC9, VA4 and VA5, which react exclusively at the TG2 transamidase site, inhibit both transamidase and GTP-binding activities. Transamidase activity is inhibited by direct inhibitor binding at the transamidase site, and GTP binding is blocked because inhibitor interaction at the transamidase site locks the protein in the extended/open conformation to disorganize/inactivate the GTP binding/GTPase site. These findings suggest that transamidase site-specific inhibitors can inhibit GTP binding/signalling by driving a conformation change that disorganizes the TG2 GTP binding to reduce TG2-dependent signalling, and that drugs designed to target this site may be potent anti-cancer agents.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 13 / 14 / 14/33 / 38/35 / 631/532/71 / 631/67/1813/1352 / Aminoacyltransferases - antagonists & inhibitors / Aminoacyltransferases - chemistry / Antineoplastic Agents - pharmacology / Antitumor agents / Apoptosis / Binding sites / Binding Sites - drug effects / Cancer / Cancer cells / Catalytic Domain - drug effects / Catalytic Domain - genetics / Cell Biology / Cell migration / Cell survival / Cell Survival - drug effects / Cell Survival - genetics / Cells, Cultured / Gene Knockout Techniques / Genetic aspects / GTP-Binding Proteins - antagonists & inhibitors / GTP-Binding Proteins - chemistry / GTP-Binding Proteins - genetics / GTP-Binding Proteins - metabolism / Guanosine triphosphatases / Guanosine triphosphate / Guanosine Triphosphate - metabolism / Health aspects / Human Genetics / Humans / Internal Medicine / Medicine / Medicine & Public Health / Molecular Targeted Therapy / Neoplastic Stem Cells - drug effects / Neoplastic Stem Cells - physiology / Oncology / original-article / Protein binding / Protein Binding - drug effects / Protein Conformation - drug effects / Protein Glutamine gamma Glutamyltransferase 2 / Proteins / Stem cells / Transglutaminase 2 / Transglutaminases - antagonists & inhibitors / Transglutaminases - chemistry / Transglutaminases - genetics / Transglutaminases - metabolism / Tumor proteins / Tumors