Inhibitory effect of HIV-1 Tat protein on the sodium-D-glucose symporter of human intestinal epithelial cells.
OBJECTIVE
The pathophysiology of HIV-1-related intestinal dysfunction is largely unknown. We previously found that the transactivator factor peptide (Tat) produced by HIV-1 induces ion secretion and inhibits cell proliferation in human enterocytes. Because sugar malabsorption is a frequent feature in AIDS patients, we evaluated whether Tat inhibits intestinal glucose absorption.


METHODS
We measured Na-D-glucose symporter (SGLT-1) activity and determined its phenotypic expression in Caco-2 cells, in the presence and absence of Tat, in uptake experiments using a non-metabolized radiolabelled glucose analogue, and by western blot analysis, respectively. alpha-Tubulin staining was used to study the effects exerted by Tat on cell structure.


RESULTS
Tat dose dependently inhibited glucose uptake by human enterocytes. This effect was prevented by anti-Tat polyclonal antibodies and by L-type Ca channels agonist Bay K8644. Western blot analysis of cellular lysates and brush-border membrane preparations showed that Tat induced SGLT-1 missorting. Tat also caused a dramatic decrease in alpha-tubulin staining, which indicates dysruption of the cytoskeleton organization.


CONCLUSIONS
Tat acutely impairs intestinal glucose absorption through SGLT-1 missorting. This result indicates that Tat is directly involved in AIDS-associated intestinal dysfunction.
Canani
Roberto Berni
RB
Department of Pediatrics, University Federico II of Naples, Italy.
De Marco
Giulio
G
Passariello
Annalisa
A
Buccigrossi
Vittoria
V
Ruotolo
Serena
S
Bracale
Ileana
I
Porcaro
Francesco
F
Bifulco
Giuseppe
G
Guarino
Alfredo
A
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D015415:Biomarkers / Q000032:analysis; D015153:Blotting, Western / Q000379:methods; D018938:Caco-2 Cells; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D003470:Culture Media; D003599:Cytoskeleton / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D015696:Gene Products, tat / Q000494:pharmacology*; D005947:Glucose / Q000493:pharmacokinetics; D015497:HIV-1 / Q000737:chemistry*; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D051269:Sodium-Glucose Transporter 1 / Q000032:analysis / Q000378:metabolism*; D014404:Tubulin / Q000032:analysis; D054322:tat Gene Products, Human Immunodeficiency Virus
D015415:Biomarkers; D002120:Calcium Channel Agonists; D015220:Calcium Channels; D003470:Culture Media; D015696:Gene Products, tat; D051269:Sodium-Glucose Transporter 1; D014404:Tubulin; D054322:tat Gene Products, Human Immunodeficiency Virus; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D005947:Glucose