title: Filopodia formation via a specific Eph family member and PI3K in immortalized cholangiocytes.
abstract: Biliary ducts are lined with epithelial cells, which consist of at least two types of cholangiocytes, small and large. In contrast to large cholangiocytes, which are involved in secretion, the role of small cholangiocytes has not been elucidated. To address this question, we analyzed the migration-based characteristics of these cells that may help to understand their functions in vivo. Interestingly, dibutyryl cAMP induced marked filopodia formation and cdc42 activation in the normal mouse cholangiocyte (NMC)-small cell line compared with the NMC-large cell line. Analysis of members of the ephrin (Eph)A family of guidance molecules revealed a distinct subcellular distribution of EphA5 and EphA8 members: EphA8 was equally expressed by both cell types and localized subcellularly in peripheral cell membranes, whereas EphA5 was expressed predominantly in NMC-S and localized to filopodia. Moreover, cAMP-inducible filopodia formation in these cells was abrogated using EphA5 short interfering RNA. Finally, we found that the Rho family GTPase cdc42 was activated in a manner dependent on EphA5. Wortmannin, a specific inhibitor of phosphotidylinositol 3-kinase (PI3K), abolished the activation of cdc42 dependent on EphA5, suggesting the involvement of PI3K in the EphA5-cdc42 pathway. Together, our findings suggest a cAMP-EphA5-cdc42-dependent regulation of small cholangiocyte migration, which are anticipated to facilitate the understanding of the nature of cholangiocytes and to explain certain general aspects of cAMP-cdc42 activation signaling with regard to cell morphogenesis.
authors.affiliation: Division of Gastroenterology, Tohoku University School of Medicine, 1-1 Seiryo Aoba, Sendai 980-8574, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Fukushima
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ueno
authors.forename: Jun
authors.initials: J
authors.lastname: Inoue
authors.forename: Noriatsu
authors.initials: N
authors.lastname: Kanno
authors.forename: Tooru
authors.initials: T
authors.lastname: Shimosegawa
mesh_terms: D000818:Animals; D001652:Bile Ducts / Q000166:cytology* / Q000201:enzymology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D005822:Genetic Vectors; D015151:Immunoblotting; D007633:Keratins / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D011554:Pseudopodia / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000235:genetics; D036081:Receptors, Eph Family / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000502:physiology
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D007633:Keratins; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D036081:Receptors, Eph Family; D020764:cdc42 GTP-Binding Protein