title: Mannose phosphate isomerase regulates fibroblast growth factor receptor family signaling and glioma radiosensitivity.
abstract: Asparagine-linked glycosylation is an endoplasmic reticulum co- and post-translational modification that enables the transit and function of receptor tyrosine kinase (RTK) glycoproteins. To gain insight into the regulatory role of glycosylation enzymes on RTK function, we investigated shRNA and siRNA knockdown of mannose phosphate isomerase (MPI), an enzyme required for mature glycan precursor biosynthesis. Loss of MPI activity reduced phosphorylation of FGFR family receptors in U-251 and SKMG-3 malignant glioma cell lines and also resulted in significant decreases in FRS2, Akt, and MAPK signaling. However, MPI knockdown did not affect ligand-induced activation or signaling of EGFR or MET RTKs, suggesting that FGFRs are more susceptible to MPI inhibition. The reductions in FGFR signaling were not caused by loss of FGF ligands or receptors, but instead were caused by interference with receptor dimerization. Investigations into the cellular consequences of MPI knockdown showed that cellular programs driven by FGFR signaling, and integral to the clinical progression of malignant glioma, were impaired. In addition to a blockade of cellular migration, MPI knockdown also significantly reduced glioma cell clonogenic survival following ionizing radiation. Therefore our results suggest that targeted inhibition of enzymes required for cell surface receptor glycosylation can be manipulated to produce discrete and limited consequences for critical client glycoproteins expressed by tumor cells. Furthermore, this work identifies MPI as a potential enzymatic target for disrupting cell surface receptor-dependent survival signaling and as a novel approach for therapeutic radiosensitization.
authors.affiliation: Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Cazet
authors.affiliation: Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Charest
authors.affiliation: Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Bennett
authors.affiliation: Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Cecilia Lopez
authors.initials: CL
authors.lastname: Sambrooks
authors.affiliation: Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Joseph N
authors.initials: JN
authors.lastname: Contessa
mesh_terms: D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D055785:Gene Knockdown Techniques; D005910:Glioma / Q000235:genetics / Q000378:metabolism* / Q000532:radiotherapy; D006801:Humans; D008359:Mannose-6-Phosphate Isomerase / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization; D021381:Protein Transport; D034741:RNA, Small Interfering; D011836:Radiation Tolerance / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D034741:RNA, Small Interfering; D017468:Receptors, Fibroblast Growth Factor; D020794:Receptor Protein-Tyrosine Kinases; D051497:Receptor, Fibroblast Growth Factor, Type 2; D008359:Mannose-6-Phosphate Isomerase