Expression of GTP-dependent and GTP-independent Tissue-type Transglutaminase in Cytokine-treated Rat Brain Astrocytes

Abstract

Tissue-type transglutaminases (TGases) were recently shown to exert dual enzymatic activities; they catalyze the posttranslational modification of proteins by transamidation, and they also act as guanosine triphosphatase (GTPase). Here we show that a tissue-type TGase is expressed in rat brain astrocytes in vitro, and is induced by the inflammation-associated cytokines interleukin-1␤ and to a lesser extent by tumor necrosis factor-␣. Induction is accompanied by overexpression and appearance of an additional shorter clone, which does not contain the long 3 -untranslated region and encodes for a novel TGase enzyme whose C terminus lacks a site that affects the enzyme's interaction with guanosine triphosphate (GTP). Expression of two clones revealed that the long form is inhibited noncompetitively by GTP, but the short form significantly less so. The different affinities for GTP may account for the difference in physiological function between these two enzymes.

GTP Binding and Signaling by Gh/Transglutaminase II Involves Distinct Residues in a Unique GTP-binding Pocket

“…2, A and C) and to an additional region (residues 465-589 in barrel 1). These data agree with previous work that localized GTP binding to residues 139 -185 of the core (25) and implicated residues 517-523 of barrel 1 in stabilization of GTP binding (26). The conservation of residues 159 -173 in the type II TGases of various species (but not in fXIIIA; TGases I, III, or IV; or band 4.2 (Fig.…”

“…Models of G h (25,26) based on the crystal structure of fXIIIA predict that this region is distinct from, yet in close proximity to, the TGase active site. It is also in close proximity to residues 517-523 of barrel 1 that are involved in stabilization of GTP binding (26).…”

“…Models of G h (25,26) based on the crystal structure of fXIIIA predict that this region is distinct from, yet in close proximity to, the TGase active site. It is also in close proximity to residues 517-523 of barrel 1 that are involved in stabilization of GTP binding (26). Mutation of the active site Cys to Ser (C277S) abolished TGase activity without affecting signaling (10), indicating that although the TGase and GTP-binding sites are allosterically linked, signaling can function independently of TGase activity.…”

Transglutaminase 2 expression induced by lipopolysaccharide stimulation together with NO synthase induction in cultured astrocytes

“…TG activity has been detected in cultured rat astrocytes as well as neurons (Campisi et al, 1992;Monsonego et al, 1997). Interestingly, TG2 expression in astrocytes is induced by inflammation-associated cytokines such as IL-1β and TNF-α (Monsonego et al, 1997).…”

“…Interestingly, TG2 expression in astrocytes is induced by inflammation-associated cytokines such as IL-1β and TNF-α (Monsonego et al, 1997). On the other hand, lipopolysaccharide (LPS) is well known to activate cultured astrocytes inducing iNOS expression (Murakami et al, 2003) and proinflammatory cytokines (Faure et al, 2001;Martin et al, 2006).…”