title: Opposing effects of two tissue transglutaminase protein isoforms in neuroblastoma cell differentiation.
abstract: We have demonstrated previously that the Myc oncoprotein blocks cancer cell differentiation by forming a novel transcriptional repressor complex with histone deacetylase and inhibiting gene transcription of tissue transglutaminase (TG2). Moreover, induction of TG2 gene transcription and transamidase activity is essential for the differentiating effects of retinoids in cancer cells. Here, we show that two structurally distinct TG2 protein isoforms, the full-length (TG2-L) and the short form (TG2-S), exert opposing effects on cell differentiation. Repression of TG2-L with small interfering RNA, which did not affect TG2-S expression, induced dramatic neuritic differentiation in neuroblastoma cells. In contrast, overexpression of TG2-S or a GTP-binding-deficient mutant of TG2-L (R580A), both of which lack the GTP-binding Arg-580 residue, induced neuroblastoma cell differentiation, which was blocked by an inhibitor of transamidase activity. Whereas N-Myc repressed and retinoid activated both TG2 isoforms, repression of TG2-L, but not simultaneous repression of TG2-L and TG2-S, enhanced neuroblastoma cell differentiation due to N-Myc small interfering RNA or retinoid. Moreover, suppression of vasoactive intestinal peptide (VIP) expression alone induced neuroblastoma cell differentiation, and VIP was up-regulated by TG2-L, but not TG2-S. Taken together, our data indicate that TG2-L and TG2-S exert opposite effects on cell differentiation due to differences in GTP binding and modulation of VIP gene transcription. Our findings highlight the potential importance of repressing the GTP binding activity of TG2-L or activating the transamidase activity of TG2-L or TG2-S for the treatment of neuroblastoma, and possibly also other Myc-induced malignancies, and for enhancing retinoid anticancer effects.
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031.
authors.forename: Andrew E L
authors.initials: AEL
authors.lastname: Tee
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031; the Centre for Children's Cancer and Blood Disorders, Sydney Children's Hospital, Sydney, New South Wales 2031 and.
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Marshall
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031.
authors.forename: Pei Y
authors.initials: PY
authors.lastname: Liu
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031.
authors.forename: Ning
authors.initials: N
authors.lastname: Xu
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031.
authors.forename: Michelle
authors.initials: M
authors.lastname: Haber
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031.
authors.forename: Murray D
authors.initials: MD
authors.lastname: Norris
authors.affiliation: the Victor Chang Cardiac Research Institute, University of New South Wales, Sydney, New South Wales 2050, Australia.
authors.forename: Siiri E
authors.initials: SE
authors.lastname: Iismaa
authors.affiliation: From the Children's Cancer Institute Australia, Sydney Children's Hospital, Sydney, New South Wales 2031. Electronic address: tliu@ccia.unsw.edu.au.
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
mesh_terms: D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D019204:GTP-Binding Proteins; D015971:Gene Expression Regulation, Enzymologic; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D016501:Neurites / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D009447:Neuroblastoma / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D011485:Protein Binding; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012176:Retinoids / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000235:genetics / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D016271:Proto-Oncogene Proteins c-myc; D012176:Retinoids; D014660:Vasoactive Intestinal Peptide; D006160:Guanosine Triphosphate; D001120:Arginine; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins