The adenine nucleotide translocator 1 acts as a type 2 transglutaminase substrate: implications for mitochondrial-dependent apoptosis

Abstract

In this study we provide in vitro and in vivo evidence showing that the protein disulphide isomerase (PDI) activity of type 2 transglutaminase (TG2) regulates the correct assembly and function of the mitochondrial ADP/ATP transporter adenine nucleotide translocator 1 (ANT1). We demonstrate, by means of biochemical and morphological analyses, that ANT1 and TG2 physically interact in the mitochondria. Under physiological conditions, TG2's PDI activity regulates the ADP/ATP transporter function by controlling the oligomerization of ANT1. In fact, mitochondria isolated from hearts of TG2 À/À mice exhibit increased polymerization of ANT1, paralleled by an enhanced ADP/ATP carrier activity, as compared to mitochondria belonging to TG2 þ / þ mice. Interestingly, upon cell-death induction, ANT1 becomes a substrate for TG2's cross-linking activity and the lack of TG2 results in a reduction of apoptosis as well as in a marked sensitivity to the ADP/ATP exchange inhibition by atractyloside. These findings suggest a complex TG2-dependent regulation of the ADP/ATP transporter and reveal new important avenues for its potential applications in the treatment of some mitochondrial-dependent diseases, including cardiovascular and neurodegenerative diseases.

Transglutaminase 2 ablation leads to mitophagy impairment associated with a metabolic shift towards aerobic glycolysis

“…13,25 In keeping with this notion, some of the characterized TG2 substrates (Prohibitin, ATP synthase b, ANT-1) play a key role in the mitochondrial homeostasis. 26,14 Prompted by such evidence, we decided to study a possible role of the enzyme in mitochondrial homeostasis, with particular regard to removal of dysfunctional mitochondria by autophagy and its impact on the overall cellular metabolism. To this end, we used MEFs obtained from wild-type (WT MEFs) and TG2 knockout (KO MEFs) mice and HEK293 cells stably transfected with the WT enzyme (HEK293 TG2 ) 23 Figures S1A and B).…”

“…12 More recently, TG2 has also been reported to possess intracellular serine/threonine kinase and protein disulphide isomerase activity (PDI). 13,14 The PDI enzymatic activity has been shown to lead to the post-translational modification of key mitochondrial proteins. [15][16][17][18][19] Given the TG2 ubiquitous expression and variety of enzymatic and nonenzymatic activities, it is not surprising that this protein appears intimately involved in the regulation of numerous cell functions including cell adhesion, migration, survival and death, exocytosis and more recently autophagy.…”

Adenine nucleotide translocase: a component of the phylogenetically conserved cell death machinery

“…59 Malorni et al provide evidence that ANT1 and TG2 physically interact at mitochondria, and that the protein disulfide isomerase activity of TG2 is important to limit ANT1 oligomerization in physiological conditions, thereby controlling the vital function of ANT1 as an ATP/ADP antiporter. Moreover, TG2 appears to be required for (or at least to contribute to) the induction of cell death by multiple triggers, including the glycolysis inhibitor deoxy-D-glucose (DDG) and STS.…”

“…These data suggest that, at least in some experimental settings, TG2 might be mandatory to enable and/or stabilize the association of Bax with ANT1. 59 …”

Adenine nucleotide translocase family: four isoforms for apoptosis modulation in cancer

“…Later, a second breakthrough highlighted the critical involvement of ANT in the execution of the mitochondrial apoptosis pathway in various pathophysiological and experimental models, such as ischemiareperfusion, intoxication and chemotherapy (Marzo et al, 1998a;Cao et al, 2001;Haouzi et al, 2002;Malorni et al, 2009). For instance, ANT could influence cell death through cooperation with pro-apoptotic proteins such as Bax, viral proteins (for example viral protein R (Vpr) from HIV-1, PB1-F2 from Influenza) or through participation in a mitochondrial polyprotein complex, the so-called permeability transition pore complex (PTPC) in diverse model systems such as human carcinoma cell lines, cardiomyocytes and neurons (Crompton, 1999;Cao et al, 2001;De Giorgi et al, 2002;Brenner and Grimm, 2006) (Figure 1).…”