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Regulation of Phosphoglucose Isomerase/Autocrine Motility Factor Activities by the Poly(ADP-Ribose) Polymerase Family-14

¹ Tumor Progression and Metastasis Program, Karmanos Cancer Institute, School of Medicine, Wayne State University, Detroit, Michigan; Departments of ² Orthopaedic Surgery and ³ General Surgical Science (Surgery I), School of Medicine, and ⁴ Department of Physical Therapy, School of Health Science, Gunma University, Gunma, Japan

Requests for reprints: Avraham Raz, Tumor Progression and Metastasis Program, Karmanos Cancer Institute, School of Medicine, Wayne State University, 110 East Warren Avenue, Detroit, MI 48201. Phone: 313-833-0960; Fax: 313-831-7518; E-mail: raza{at}karmanos.org.

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a ubiquitous cytosolic enzyme essential for glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine [autocrine motility factor (AMF)] eliciting mitogenic, motogenic, and differentiation functions through binding to its cell surface receptor gp78/AMF receptor (AMFR). AMFR contains a seven-transmembrane domain with RING-H2 and leucine zipper motifs showing ubiquitin protein ligase (E3) activity and is exposed on the endoplasmic reticulum surface. Augmented expressions of both PGI/AMF and AMFR have been implicated in tumor progression and metastasis, and an intracellular binding partner of PGI/AMF is expected to regulate in part its diverse biological functions. Thus, we screened a cDNA library using a yeast two-hybrid system to search for interacting protein(s) and report on the finding of poly(ADP-ribose) polymerase-14 (PARP-14) to be a binding partner with PGI/AMF. PARP-14–PGI/AMF interaction was confirmed by coimmunoprecipitation and immunolocalization. We also report that PGI/AMF degradation is mainly regulated by the ubiquitin-lysosome system and RNA interference experiments revealed that PARP-14 inhibits PGI/AMF ubiquitination, thus contributing to its stabilization and secretion. This newly characterized PARP-14 protein should assist in understanding the regulation of PGI/AMF intracellular function(s) and may provide a new therapeutic target for inhibition of PGI/AMF inducing tumor cell migration and invasion during metastasis. [Cancer Res 2007;67(18):8682–9]