title: A mediator of Rho-dependent invasion moonlights as a methionine salvage enzyme.
abstract: RhoA controls changes in cell morphology and invasion associated with cancer phenotypes. Cell lines derived from melanoma tumors at varying stages revealed that RhoA is selectively activated in cells of metastatic origin. We describe a functional proteomics strategy to identify proteins regulated by RhoA and report a previously uncharacterized human protein, named "mediator of RhoA-dependent invasion (MRDI)," that is induced in metastatic cells by constitutive RhoA activation and promotes cell invasion. In human melanomas, MRDI localization correlated with stage, showing nuclear localization in nevi and early stage tumors and cytoplasmic localization with plasma membrane accentuation in late stage tumors. Consistent with its role in promoting cell invasion, MRDI localized to cell protrusions and leading edge membranes in cultured cells and was required for cell motility, tyrosine phosphorylation of focal adhesion kinase, and modulation of actin stress fibers. Unexpectedly MRDI had enzymatic function as an isomerase that converts the S-adenosylmethionine catabolite 5-methylribose 1-phosphate into 5-methylribulose 1-phosphate. The enzymatic function of MRDI was required for methionine salvage from S-adenosylmethionine but distinct from its function in cell invasion. Thus, mechanisms used by signal transduction pathways to control cell movement have evolved from proteins with ancient function in amino acid metabolism.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
authors.forename: Yukihito
authors.initials: Y
authors.lastname: Kabuyama
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Litman
authors.forename: Paul D
authors.initials: PD
authors.lastname: Templeton
authors.forename: Sandra I
authors.initials: SI
authors.lastname: Metzner
authors.forename: Eric S
authors.initials: ES
authors.lastname: Witze
authors.forename: Gretchen M
authors.initials: GM
authors.lastname: Argast
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Langer
authors.forename: Kirsi
authors.initials: K
authors.lastname: Polvinen
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Shellman
authors.forename: Daniel
authors.initials: D
authors.lastname: Chan
authors.forename: John B
authors.initials: JB
authors.lastname: Shabb
authors.forename: James E
authors.initials: JE
authors.lastname: Fitzpatrick
authors.forename: Katheryn A
authors.initials: KA
authors.lastname: Resing
authors.forename: Marcelo C
authors.initials: MC
authors.lastname: Sousa
authors.forename: Natalie G
authors.initials: NG
authors.lastname: Ahn
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D008545:Melanoma / Q000201:enzymology / Q000473:pathology; D008715:Methionine / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D040901:Proteomics / Q000379:methods; D034622:RNA Interference; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014183:Transplantation, Heterologous; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D012436:S-Adenosylmethionine; D008715:Methionine; D020742:rhoA GTP-Binding Protein; D019747:Aldose-Ketose Isomerases; C546404:MRI1 protein, human