Phosphoglycerate mutase (PGAM) is an enzyme of intermediary metabolism that converts 3-phosphoglycerate to 2-phosphoglycerate in glycolysis. Here, we discovered PGAM5 that is anchored in the mitochondrial membrane lacks PGAM activity and instead associates with the MAP kinase kinase kinase ASK1 and acts as a specific protein Ser/Thr phosphatase that activates ASK1 by dephosphorylation of inhibitory sites. Mutation of an active site His-105 in PGAM5 abolished phosphatase activity with ASK1 and phospho-Thr peptides as substrates. The Drosophila and Caenorhabditis elegans orthologs of PGAM5 also exhibit specific Ser/Thr phosphatase activity and activate the corresponding Drosophila and C. elegans ASK1 kinases. PGAM5 is unrelated to the other known Ser/Thr phosphatases of the PPP, MPP, and FCP families, and our results suggest that this member of the PGAM family has crossed over from small molecules to protein substrates and been adapted to serve as a specialized activator of ASK1.MAP kinase ͉ protein phosphatase P hosphoglycerate mutase (PGAM) is an evolutionarily conserved enzyme of intermediary metabolism that converts 3-phosphoglycerate (3PG) to 2-phosphoglycerate (2PG) in glycolysis and the founder member of the PGAM protein family (1). Members of this family share a common catalytic domain, designated as the PGAM domain, and function as phosphotransferases and/or phosphohydrolases with small molecule substrates. For instance, 1,3-and 1,2-bisphosphoglycerate and fructose-2,6-bisphosphate are the substrates of well-characterized members of this family, the bisphosphoglycerate mutase (BPGM) and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFKFB), respectively. The catalytic core of the PGAM domain centers on a histidine residue that acts as a phospho accepter during catalysis. These biochemical and structural features are also shared with the histidine acid phosphatase family of enzymes, and it has recently been proposed that these 2 families can be integrated into a histidine phosphatase superfamily (2). Whereas members of this superfamily predominantly target small molecule substrates, prostatic acid phosphatase has been shown to catalyze hydrolysis of high energy Phospho-Tyr bonds in substrates such as ErbB2 and EGF receptor (3, 4). In addition, Sts-1/TULA-2 in the PGAM family has been shown to function as a protein tyrosine phosphatase, dephosphorylating tyrosine kinases ZAP-70, Syk, and EGF receptor (5-7). These results open the possibility that enzymes in the PGAM family might regulate cellular functions beyond those in glucose metabolism.PGAM5 is a member of the PGAM family that has been shown to interact with Bcl-X L , an apoptosis regulator (8), and Keap1, a redox-regulated substrate adaptor for a cullindependent ubiquitin ligase complex (9). Although it has been suggested that the latter interaction is involved in the regulation of gene expression by the transcription factor Nrf2 (10), molecular functions of PGAM5 have not been elucidated. In this study, we identified PGAM5 as an interacting p...

Apoptosis signal-regulating kinase 1 (ASK1) is a member of the mitogen-activated protein 3-kinase family that activates both c-Jun NH2-terminal kinase and p38 pathways in response to inflammatory cytokines and physicochemical stress. We report that ASK1 deficiency in mice results in dramatic retardation of wounding-induced hair regrowth in skin. Oligonucleotide microarray analysis revealed that expression of several chemotactic and activating factors for macrophages, as well as several macrophage-specific marker genes, was reduced in the skin wound area of ASK1-deficient mice. Intracutaneous transplantation of cytokine-activated bone marrow-derived macrophages strongly induced hair growth in both wild-type and ASK1-deficient mice. These findings indicate that ASK1 is required for wounding-induced infiltration and activation of macrophages, which play central roles in inflammation-dependent hair regrowth in skin.

Abbreviations used in this paper: ASK1, apoptosis signal-regulating kinase 1; BMDM, bone marrow-derived macrophage; DC, dendritic cell; ERK, extracellular signal-regulated kinase; IL, interleukin; MCP-1, monocyte chemoattractant protein-1; MEF, mouse embryonic fi broblast; MHC, major histocompatability complex; MIP-1α, macrophage infl ammatory protein-1α; MSP, macrophagestimulating factor; WT, wild-type.The online version of this article contains supplemental material.

The human body is continuously exposed to a wide variety of physical, chemical, and biological stress stimuli from both the external and internal environments. In order to adapt to or resist stress, cells are equipped with multiple signaling systems, which elicit a wide range of stress responses. Stress signaling also operates to eliminate cells with severe stress-induced damage through the induction of apoptosis. Once stress signaling is compromised in certain adverse conditions, however, cells exhibit aberrant responses to stress, which can eventually cause various diseases including cancer. In the present review, the authors focus on the current understanding of the critical linkage between stress signaling and cancer.