Serotonin modifies cytoskeleton and brush-border membrane architecture in human intestinal epithelial cells

Ravinder K. Gill, Le Shen, Jerrold R. Turner, Seema Saksena, Waddah A. Alrefai, Nitika Pant, Ali Esmaili, Alka Dwivedi, Krishnamurthy Ramaswamy, Pradeep K. Dudeja

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 μM, 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 Ca2+ and PKCα inhibition (Go6976). In vitro assays revealed that PKCα 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 Ca2+ and PKCα-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.

  • microvilli
  • serotonin and actin
  • 5-HT and curvature
  • stress fibers
  • ion transporter
  • cytoskeleton
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