title: The critical interaction of the metallopeptidase PHEX with heparan sulfate proteoglycans.
abstract: The PHEX gene (phosphate-regulating gene with homologies to endopeptidase on the X chromosome) identified as a mutated gene in patients with X-linked hypophosphatemia (XLH), encodes a protein (PHEX) that shows striking homologies to members of the M13 family of zinc metallopeptidases. In the present work the interaction of glycosaminoglycans with PHEX has been investigated by affinity chromatography, circular dichroism, protein intrinsic fluorescence analysis, hydrolysis of FRET substrates flow cytometry and confocal microscopy. PHEX was eluted from a heparin-Sepharose chromatography column at 0.8 M NaCl showing a strong interaction with heparin. Circular dichroism spectra and intrinsic fluorescence analysis showed that PHEX is protected by glycosaminoglycans against thermal denaturation. Heparin, heparan sulfate and chondroitin sulfate inhibited PHEX catalytic activity, however among them, heparin presented the highest inhibitory activity (Ki=2.5+/-0.2 nM). Flow cytometry analysis showed that PHEX conjugated to Alexa Fluor 488 binds to the cell surface of CHO-K1, but did not bind to glycosaminoglycans defective cells CHO-745. Endogenous PHEX was detected at the cell surface of CHO-K1 colocalized with heparan sulfate proteoglycans, but was not found at the cell surface of glycosaminoglycans defective cells CHO-745. In permeabilized cells, PHEX was detected in endoplasmic reticulum of both cells. In addition, we observed that PHEX colocalizes with heparan sulfate at the cell surface of osteoblasts. This is the first report that the metallopeptidase PHEX is a heparin binding protein and that the interaction with GAGs modulates its enzymatic activity, protein stability and cellular trafficking.
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo 04044-020, SP, Brazil.
authors.forename: Nilana M T
authors.initials: NM
authors.lastname: Barros
authors.forename: Fabio D
authors.initials: FD
authors.lastname: Nascimento
authors.forename: Vitor
authors.initials: V
authors.lastname: Oliveira
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: Juliano
authors.forename: Luiz
authors.initials: L
authors.lastname: Juliano
authors.forename: Thomas
authors.initials: T
authors.lastname: Loisel
authors.forename: Helena B
authors.initials: HB
authors.lastname: Nader
authors.forename: Guy
authors.initials: G
authors.lastname: Boileau
authors.forename: Ivarne L S
authors.initials: IL
authors.lastname: Tersariol
authors.forename: Adriana K
authors.initials: AK
authors.lastname: Carmona
mesh_terms: D000818:Animals; D016466:CHO Cells; D002846:Chromatography, Affinity; D002942:Circular Dichroism; D006224:Cricetinae; D003412:Cricetulus; D031541:Fluorescence Resonance Energy Transfer; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism / Q000494:pharmacology; D006497:Heparan Sulfate / Q000378:metabolism / Q000502:physiology; D006868:Hydrolysis; D045726:Metalloproteases / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D019812:Heparan Sulfate Proteoglycans; D006493:Heparin; D006497:Heparan Sulfate; D045726:Metalloproteases; D011506:Proteins; D011509:Proteoglycans; D011994:Recombinant Proteins