Gh(alpha)/tissue transglutaminase 2: an emerging G protein in signal transduction

Gh protein is an heterodimer made up of two subunits (alpha) and (beta). Different from the traditional monomeric and heterotrimeric G proteins, Gh(alpha) subunit exhibits both GTPase and transglutaminase activities whereas Gh(beta) was identified as calreticulin. Activation of Gh by G protein-coupled receptors (GPCR) turns off transglutaminase activity and shifts Gh(alpha) to signal transducer. Thereafter, Gh(alpha) regulates downstream effectors. All these aspects are discussed in the present review, in order to shed new light on this atypical G protein.