Identification of a Class of Protein ADP-Ribosylating Sirtuins in Microbial Pathogens

Abstract

SummarySirtuins are an ancient family of NAD+-dependent deacylases connected with the regulation of fundamental cellular processes including metabolic homeostasis and genome integrity. We show the existence of a hitherto unrecognized class of sirtuins, found predominantly in microbial pathogens. In contrast to earlier described classes, these sirtuins exhibit robust protein ADP-ribosylation activity. In our model organisms, Staphylococcus aureus and Streptococcus pyogenes, the activity is dependent on prior lipoylation of the target protein and can be reversed by a sirtuin-associated macrodomain protein. Together, our data describe a sirtuin-dependent reversible protein ADP-ribosylation system and establish a crosstalk between lipoylation and mono-ADP-ribosylation. We propose that these posttranslational modifications modulate microbial virulence by regulating the response to host-derived reactive oxygen species.

ADP‐ribosylation: new facets of an ancient modification

“…There are seven sirtuin proteins operating in human cells , their primary enzymatic activity is protein deacetylation producing O ‐acetyl‐ADP‐ribose ( O AADPr) metabolite as a by‐product of its ART reaction . Sirtuins can sometimes directly modify proteins (Fig. ).…”

“…). Some macrodomains have also evolved enzymatic activity and are capable of hydrolysing ADP‐ribosylation (see below) . As a consequence, macrodomain‐containing proteins are involved in a diverse set of cellular functions, such as chromatin remodelling and DNA‐damage repair, oxidative stress response, metabolic processes and pathogenic mechanisms .…”

“…Studies looking either at the genomic context of ADP‐ribosylating systems or their evolution in bacteria suggest that ADP‐ribosylation might be involved in the regulation of many crucial cellular processes including bacterial persistence, oxidative stress response and adaptation to the host environment in general .…”

“…SirTM is encoded within an operon containing a modification carrier protein (GcvH‐L). GcvH‐L becomes doubly modified by two different PTMs through the actions of SirTM (ADP‐ribosylation) and another component of the operon that acts as a lipoate ligase (synthesising the protein lipoylation) . Yet another protein product of the same operon is a macrodomain protein (belonging to the MacroD‐type class), which specifically reverses the ADP‐ribosylation of GcvH‐L .…”

Generating Protein-Linked and Protein-Free Mono-, Oligo-, and Poly(ADP-Ribose) In Vitro

“…The modification is catalyzed by a diverse family of ADP-ribosyltransferase (ART) enzymes, including (1) bacterial toxins (e.g., Cholera and Diphtheria toxins) [6, 28], (2) ecto-ADP-ribosyltransferases (ectoARTs) [10], (3) members of the sirtuin family [13, 25, 31], and (4) members of the poly(ADP-ribose) polymerase (PARP) family [2, 8]. ARTs generally catalyze mono(ADP-ribosyl)ation (MARylation) of their substrate proteins, although some PARPs, such as PARP-1, catalyze oligo- and poly(ADP-ribosyl)ation (OARylation and PARylation, respectively) [6, 8, 10, 14, 32] (Figure 1).…”