Transglutaminase-mediated oligomerization promotes osteoblast adhesive properties of osteopontin and bone sialoprotein

Abstract

Tissue transglutaminase (TG2) is a widely distributed, protein-crosslinking enzyme having a prominent role in cell adhesion as a β1 integrin co-receptor for fibronectin. In bone and teeth, its substrates include the matricellular proteins osteopontin (OpN) and bone sialoprotein (Bsp). The aim of this study was to examine effects of TG2-mediated crosslinking and oligomerization of OpN and Bsp on osteoblast cell adhesion. We show that surfaces coated with oligomerized OpN and Bsp promote MC3T3-e1/C4 osteoblastic cell adhesion significantly better than surfaces coated with the monomeric form of the proteins. Both OpN and Bsp oligomer-adherent cells showed more cytoplasmic extensions than those cells grown on the monomer-coated surfaces indicative of increased cell connectivity. Our study suggests a role for TG2 in promoting the cell adhesion function of two matricellular substrate proteins prominent in bone, tooth cementum and certain tumors. © 2011 Landes Bioscience.