title: Cell surface heparan sulfate proteoglycans mediate the internalization of PDX-1 protein.
abstract: Although islet transplantation is a promising therapeutic option for the treatment of type 1 diabetes, the shortage of suitable donor tissues remains a major obstacle. Pancreatic stem/progenitor cells residing within the ductal epithelium have been used to generate human islet-like clusters, but there is no efficient strategy for facilitating differentiation of progenitor cells into insulin-producing cells. A previous study reported that exogenous PDX-1 protein can be transduced into pancreatic stem/progenitor cells and induce differentiation of the cells into insulin-producing cells without requiring gene transfer technology. This study provides genetic and biochemical evidence that cell membrane heparan sulfate proteoglycans are required for extracellular PDX-1 internalization. Heparin, one of the soluble glycosaminoglycans (GAGs), inhibited PDX-1 internalization, while chondroitin sulfate A, B, and C caused only very limited inhibition. Cell treatment with heparinase-III demonstrated impaired PDX-1 internalization, while treatment with chondroitinase ABC, or with chondroitinase AC, was completely ineffective in inhibiting PDX-1 internalization. Different mutant cell lines originating from CHO K1 cells and defective in GAG biosynthesis were also examined. PDX-1 internalization was significantly reduced in both pgs A-745 mutant cells, which are defective in a enzyme that initiates GAG synthesis, and pgs B-618 cells, which produce about 15% of the amount of GAGs synthesized by wild-type cells. These data indicate that cell-surface heparan sulfate proteoglycans are required for PDX-1 internalization and that PDX-1 protein transduction could be a valuable strategy for inducing insulin expression in pancreatic stem/progenitor cells without requiring gene transfer technology.
authors.affiliation: Fujita Health University, Second Department of Surgery, Aichi 470-1192, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Ueda
authors.forename: Shinichi
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Shuji
authors.initials: S
authors.lastname: Hayashi
authors.forename: Naoya
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Noguchi
mesh_terms: D000818:Animals; D016466:CHO Cells; D002454:Cell Differentiation; D006224:Cricetinae; D003412:Cricetulus; D003922:Diabetes Mellitus, Type 1 / Q000601:surgery; D019812:Heparan Sulfate Proteoglycans / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000096:biosynthesis / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000473:pathology; D007515:Islets of Langerhans / Q000378:metabolism / Q000473:pathology; D016381:Islets of Langerhans Transplantation; D021381:Protein Transport; D013234:Stem Cells / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014161:Transduction, Genetic / Q000379:methods
chemical_list: D019812:Heparan Sulfate Proteoglycans; D018398:Homeodomain Proteins; D007328:Insulin; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein