Glucose Deprivation Converts Poly(ADP-ribose) Polymerase-1 Hyperactivation into a Transient Energy-producing Process

Daniela Buonvicino,Laura Formentini,Giulia Cipriani,Alberto Chiarugi

doi:10.1074/jbc.m113.506378

Abstract

Massive poly(ADP-ribose) formation by poly(ADP-ribose) polymerase-1 (PARP-1) triggers NAD depletion and cell death. These events have been invariantly related to cellular energy failure due to ATP shortage. The latter occurs because of both ATP consumption for NAD resynthesis and impairment of mitochondrial ATP formation caused by an increase of the AMP/ADP ratio. ATP depletion is therefore thought to be an inevitable consequence of NAD loss and a hallmark of PARP-1 activation. Here, we challenge this scenario by showing that PARP-1 hyperactivation in cells cultured in the absence of glucose (Glu(-) cells) is followed by NAD depletion and an unexpected PARP-1 activity-dependent ATP increase. We found increased ADP content in resting Glu(-) cells, a condition that counteracts the increase of the AMP/ADP ratio during hyperpoly(ADP-ribosyl)ation and preserves mitochondrial coupling. We also show that the increase of ATP in Glu(-) cells is due to adenylate kinase activity, transforming AMP into ADP which, in turn, is converted into ATP by coupled mitochondria. Interestingly, PARP-1-dependent mitochondrial release of apoptosis-inducing factor (AIF) and cytochrome complex (Cyt c) is reduced in Glu(-) cells, even though cell death eventually occurs. Overall, the present study identifies basal ADP content and adenylate kinase as key determinants of bioenergetics during PARP-1 hyperactivation and unequivocally demonstrates that ATP loss is not metabolically related to NAD depletion.

Highlights

Excessive activation of enzyme poly(ADP-ribose) polymerase-1 (PARP-1) causes ATP depletion and kills cells
Our study reports that massive PAR formation is not invariantly related to ATP depletion, and availability of glucose is a key determinant of poly(ADP-ribose) polymerases (PARPs)-1-dependent energy failure
By showing that NAD loss is completely unaffected in GluϪ cells despite a concomitant increase of ATP content, we demonstrate that NAD loss does not consequentially trigger ATP depletion

Summary

Background

Excessive activation of enzyme poly(ADP-ribose) polymerase-1 (PARP-1) causes ATP depletion and kills cells. Massive poly(ADP-ribose) formation by poly(ADP-ribose) polymerase-1 (PARP-1) triggers NAD depletion and cell death These events have been invariantly related to cellular energy failure due to ATP shortage. It has been proposed that intracellular NAD depletion and continuous resynthesis are the main triggers of necrotic cell death upon hyperactivation of PARP-1 This is because NAD resynthesis through the NAD rescue pathway is an ATP-dependent process that eventually leads to energy failure. This death route, the so-called “suicide hypothesis” [13], has been validated by numerous studies showing NAD and ATP depletion in cells undergoing DNA damage-dependent PARP-1 activation [6]. We found that PARP-1 activation unexpectedly leads to a burst of energy production in cells acutely starved from glucose

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION