title: Investigation of the role of glypican 3 in liver regeneration and hepatocyte proliferation.
abstract: Glypicans are heparan sulfate proteoglycans that are bound to the cell surface by glycosylphosphatidylinositol. While six members of the glypican family are known in mammals, our study focused on glypican 3 (GPC3). Loss-of-function mutations of GPC3 result in the Simpson-Golabi-Behmel syndrome, an X-linked disorder characterized by pre- and postnatal liver and other organ overgrowth. GPC3 is overexpressed in human hepatocellular carcinoma; however, its role in normal liver regeneration and hepatocyte proliferation is unknown. Here we investigated the role of GPC3 in hepatocyte proliferation. GPC3 mRNA and protein levels begin to increase 2 days after hepatectomy with peak expression levels by day 5. In hepatocyte cultures, GPC3 reaches a plateau when hepatocyte proliferation decreases. In vitro studies using Morpholino oligonucleotides showed that blocking GPC3 expression promoted hepatocyte growth. Yeast two-hybrid assays revealed that GPC3 interacts with CD81, a member of the tetraspanin family that is reported to be involved in hepatitis C virus infection and cell proliferation. We found that CD81 levels also increased 2 days after partial hepatectomy and toward the end of regeneration. Immunofluorescence showed that CD81 and GPC3 colocalize by 2 and 6 days after hepatectomy. Co-immunoprecipitation validated the interaction of GPC3 and CD81. Our results indicate that GPC3 may be a negative regulator of liver regeneration and hepatocyte proliferation, and that this regulation may involve CD81.
authors: Department of Pathology, University of Pittsburgh School of Medicine, S-410 Biomedical Science Tower, Pittsburgh, PA 15261, USA.
authors: Bowen
authors: B
authors: Liu
authors: Shirish
authors: S
authors: Paranjpe
authors: William C
authors: WC
authors: Bowen
authors: Aaron W
authors: AW
authors: Bell
authors: Jian-Hua
authors: JH
authors: Luo
authors: Yan-Ping
authors: YP
authors: Yu
authors: Wendy M
authors: WM
authors: Mars
authors: George K
authors: GK
authors: Michalopoulos
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D055785:Gene Knockdown Techniques; D053673:Glypicans / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D022781:Hepatocytes / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D008115:Liver Regeneration / Q000235:genetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D060225:Tetraspanin 28; D020798:Two-Hybrid System Techniques
chemical_list: C554798:CD81 protein, human; C554797:Cd81 protein, rat; D053673:Glypicans; C105936:Gpc3 protein, rat; D008565:Membrane Proteins; D009479:Neuropeptides; D012333:RNA, Messenger; D060225:Tetraspanin 28