title: Serotonin modifies cytoskeleton and brush-border membrane architecture in human intestinal epithelial cells.
abstract: Serotonin or 5-hydroxytryptamine (5-HT) influences numerous functions in the gastrointestinal tract. We previously demonstrated that 5-HT treatment of Caco-2 cells inhibited Na(+)/H(+) exchangers (NHE) and Cl(-)/OH(-) exchange activities via distinct signaling mechanisms. Since regulation of several ion transporters such as NHE3 is influenced by intact cytoskeleton, we hypothesized that 5-HT modifies actin cytoskeleton and/or brush-border membrane architecture via involvement of signaling pathways. Ultrastructural analysis showed that 5-HT (0.1 muM, 1 h) treatment of Caco-2 cells caused the apical membrane to assume a convex dome shape that was associated with shortening of microvilli. To examine whether these cellular architecture changes are cytoskeleton driven, we analyzed actin cytoskeleton by fluorescence microscopy. 5-HT induced basal stress fibers with prominent cortical actin filaments via 5-HT3 and 5-HT4 receptor subtypes. This induction was partially attenuated by chelation of intracellular Ca(2+) and PKCalpha inhibition (Go6976). In vitro assays revealed that PKCalpha interacted with actin and this association was increased by 5-HT. Our data provide novel evidence that 5-HT-induced signaling via 5-HT3/4 receptor subtypes to cause Ca(2+) and PKCalpha-dependent regulation of actin cytoskeleton may play an important role in modulation of ion transporters that contribute to pathophysiology of diarrheal conditions associated with elevated levels of 5-HT.
authors.affiliation: Dept. of Medicine, Univ. of Illinois at Chicago, Medical Research Service, Jesse Brown VA Medical Center, 820 S. Damen Ave., Chicago, IL 60612, USA. rgill@uic.edu
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Gill
authors.forename: Le
authors.initials: L
authors.lastname: Shen
authors.forename: Jerrold R
authors.initials: JR
authors.lastname: Turner
authors.forename: Seema
authors.initials: S
authors.lastname: Saksena
authors.forename: Waddah A
authors.initials: WA
authors.lastname: Alrefai
authors.forename: Nitika
authors.initials: N
authors.lastname: Pant
authors.forename: Ali
authors.initials: A
authors.lastname: Esmaili
authors.forename: Alka
authors.initials: A
authors.lastname: Dwivedi
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Ramaswamy
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Dudeja
mesh_terms: D000199:Actins / Q000187:drug effects; D018938:Caco-2 Cells; D002227:Carbazoles / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000648:ultrastructure; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D008871:Microvilli / Q000187:drug effects / Q000648:ultrastructure*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051571:Protein Kinase C-alpha / Q000378:metabolism; D051745:Protein Kinase C-delta / Q000378:metabolism; D012701:Serotonin / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology*
chemical_list: D000199:Actins; D002227:Carbazoles; D017923:Sodium-Hydrogen Exchangers; C081021:Go 6976; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D012701:Serotonin; D004533:Egtazic Acid; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta