Dual role for AlF4(-)-sensitive G proteins in the function of T84 epithelial cells: transport and barrier effects.
T84 monolayers were studied to determine the effect of AlF4, an activator of heterotrimeric G proteins, on Cl-secretion and intestinal barrier function. Basolateral (but not apical) addition of AlF4- increased short-circuit current (I(sc)) and decreased transepithelial resistance. Preincubation with the heavy metal chelator deferoxamine showed that both effects were dependent on Al3+. The effect on I(sc) was abolished by the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid or in Cl(-)-free solutions, whereas the decrease in resistance was unaffected. AlF4- also increased intracellular Ca2+, as assessed via fura 2 fluorometry. AlF4- had no effect on adenosine 3',5'-cyclic monophosphate (cAMP) or guanosine 3',5'-cyclic monophosphate (cGMP) levels in T84 cells. The effect of AlF4- on transepithelial resistance was accompanied by a decrease in cellular F-actin as well as increased transepithelial fluxes of the paracellular markers mannitol and inulin. The results indicate that AlF4(-)-sensitive G proteins regulate both epithelial secretory and barrier functions, but via different pathways. AlF4- increases Cl- secretion via a Ca2+-dependent and cAMP- and cGMP-independent mechanism in T84 cells, whereas the decrease in resistance is independent of Ca2+.
Ries
J
J
Department of Medicine, School of Medicine, University of California, San Diego 92103, USA.
Stein
J
J
Traynor-Kaplan
A E
AE
Barrett
K E
KE
D000199:Actins / Q000378:metabolism; D017607:Aluminum Compounds / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D004848:Epithelium / Q000502:physiology; D005459:Fluorides / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000502:physiology*; D010539:Permeability / Q000187:drug effects; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
D000199:Actins; D017607:Aluminum Compounds; D000242:Cyclic AMP; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D006152:Cyclic GMP; D003676:Deferoxamine; D005459:Fluorides; D002118:Calcium; C032311:aluminum fluoride