title: Extracellular heat shock protein A9 is a novel interaction partner of podoplanin in oral squamous cell carcinoma cells.
abstract: In previous studies, we have shown several lines of evidence that podoplanin (PDPN) plays an important role in cell adhesion via its association with extracellular components in neoplastic conditions, though there has been no trial to search for PDPN-interaction molecules in the extracellular milieu. To screen for those molecules, we performed proteomics-based analysis using liquid chromatography-tandem mass spectrometry followed by co-immunoprecipitation for PDPN in ZK-1, an oral squamous cell carcinoma (SCC) cell system whose cell membrane molecules were cross-linked with each other in their extracellular compartments, and we identified heat shock protein (HSP) A9 as one of the extracellular PDPN bound molecules. Effects of transient PDPN knockdown by siRNA in ZK-1 were also comparatively examined for cellular behaviors in terms of HSPA9 expression and secretion. Finally, HSPA9 expression modes were immunohistochemically visualized in oral SCC tissue specimens. HSPA9 was secreted from ZK-1 cells, and the expression and secretion levels of HSPA9 gene and protein were well coordinated with those of PDPN. Immunohistochemically, HSPA9 and PDPN were co-localized in ZK-1 cells and oral SCC foci, especially in the peripheral zone. In conclusion, the results indicate that HSPA9 secreted by oral SCC cells interacts with PDPN on their cell surface in an autocrine manner and regulates their growth and invasiveness.
authors.affiliation: Division of Oral Pathology, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tsuneki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Maruyama
authors.forename: Manabu
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Ahmed
authors.initials: A
authors.lastname: Essa
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Abé
authors.forename: Hamzah
authors.initials: H
authors.lastname: Babkair
authors.forename: Jun
authors.initials: J
authors.lastname: Cheng
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Saku
mesh_terms: D019898:Autocrine Communication / Q000235:genetics; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D005109:Extracellular Matrix / Q000235:genetics / Q000473:pathology; D055785:Gene Knockdown Techniques; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009062:Mouth Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D000098853:Podoplanin
chemical_list: D018840:HSP70 Heat-Shock Proteins; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; C492001:HSPA9 protein, human; C117468:PDPN protein, human; D000098853:Podoplanin