title: pH-specific sequestration of phosphoglucose isomerase/autocrine motility factor by fibronectin and heparan sulphate.
abstract: Phosphoglucose isomerase (PGI) is a glycolytic enzyme that moonlights as a cytokine under the aliases autocrine motility factor (AMF), neuroleukin and maturation factor. The cytokine function of PGI/AMF targets multiple cell types however mechanisms that regulate and sequester this ubiquitous, circulating cytokine remain largely unidentified. PGI/AMF is shown here to exhibit fibronectin (FN)-dependent cell surface association at both neutral and acid pH. Direct PGI/AMF binding to FN and fluorescence resonance energy transfer (FRET) between PGI/AMF and FN were detected only at pH 5. At neutral pH, the interaction of PGI/AMF with FN is receptor-mediated requiring prior clathrin-dependent endocytosis. PGI/AMF and FN do not co-internalize and PGI/AMF undergoes a second round of endocytosis upon recycling to the plasma membrane indicating that recycling PGI/AMF receptor complexes associate with FN fibrils. Heparan sulphate does not affect cell association of PGI/AMF at neutral pH but enhances the FN-independent cell surface association of PGI/AMF at acid pH identifying two distinct mechanisms for PGI/AMF sequestration under acidic conditions. However, only PGI/AMF sequestration by FN at acid pH was able to stimulate cell motility upon pH neutralization identifying FN as a pH-dependent cytokine trap for PGI/AMF. The multiple ways of cellular association of PGI/AMF may represent acquired mechanisms to regulate and harness the cytokine function of PGI/AMF.
authors.affiliation: Département de pathologie et biologie cellulaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Annick
authors.initials: A
authors.lastname: Lagana
authors.forename: Jacky G
authors.initials: JG
authors.lastname: Goetz
authors.forename: Nathalie
authors.initials: N
authors.lastname: Y
authors.forename: Yoram
authors.initials: Y
authors.lastname: Altschuler
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Nabi
mesh_terms: D000818:Animals; D002417:Cattle; D004705:Endocytosis; D005353:Fibronectins / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005956:Glucose-6-Phosphate Isomerase / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D051379:Mice; D041681:NIH 3T3 Cells; D011817:Rabbits
chemical_list: D005353:Fibronectins; D005956:Glucose-6-Phosphate Isomerase; D006497:Heparan Sulfate