Heme transport exhibits polarity in Caco-2 cells: evidence for an active and membrane protein-mediated process

Aliye Uc; John B Stokes; Bradley E Britigan

doi:10.1152/ajpgi.00157.2004

Back

Journal article

Heme transport exhibits polarity in Caco-2 cells: evidence for an active and membrane protein-mediated process

Aliye Uc, John B Stokes and Bradley E Britigan

American journal of physiology: Gastrointestinal and liver physiology, Vol.287(6), pp.G1150-1157

12/2004

DOI: 10.1152/ajpgi.00157.2004

PMID: 15308469

View Online

Abstract

Heme prosthetic groups are vital for all living organisms, but they can also promote cellular injury by generating reactive oxygen species. Therefore, intestinal heme absorption and distribution should be carefully regulated. Although a human intestine brush-border heme receptor/transporter has been suggested, the mechanism by which heme crosses the apical membrane is unknown. After it enters the cell, heme is degraded by heme oxygenase-1 (HO-1), and iron is released. We hypothesized that heme transport is actively regulated in Caco-2 cells. Cells exposed to hemin from the basolateral side demonstrated a higher HO-1 induction than cells exposed to hemin from the apical surface. Hemin secretion was more rapid than absorption, and net secretion occurred against a concentration gradient. Treatment of the apical membrane with trypsin increased hemin absorption by threefold, but basolateral treatment with trypsin had no effect on hemin secretion. Neither apical nor basolateral trypsin changed the paracellular pathway. We conclude that heme is acquired and transported in both absorptive and secretory directions in polarized Caco-2 cells. Secretion is via an active metabolic/transport process. Trypsin applied to the apical surface increased hemin absorption, suggesting that protease activity can uncover a process for heme uptake that is otherwise quiescent. These processes may be involved in preventing iron overload in humans.

Caco-2 Cells

Cell Survival - drug effects

Epithelial Cells - metabolism

Heme - metabolism

Heme - secretion

Electrophoresis, Polyacrylamide Gel

Epithelial Cells - drug effects

Humans

Intestinal Absorption - drug effects

Protoporphyrins - pharmacology

Electrophysiology

Porphyrins - chemical synthesis

Immunoblotting

Porphyrins - metabolism

Porphyrins - pharmacology

Hemin - metabolism

Trypsin - pharmacology

Biological Transport, Active - physiology

Mannitol - metabolism

Protein Binding

Membrane Proteins - metabolism

Heme Oxygenase (Decyclizing) - metabolism

Intestinal Absorption - physiology

Details

Title: Subtitle: Heme transport exhibits polarity in Caco-2 cells: evidence for an active and membrane protein-mediated process
Creators: Aliye Uc - Department of Pediatrics, Veterans Administration Medical Center, University of Iowa, Iowa City, IA 52242, USA. aliye-uc@uiowa.edu
John B Stokes
Bradley E Britigan
Resource Type: Journal article
Publication Details: American journal of physiology: Gastrointestinal and liver physiology, Vol.287(6), pp.G1150-1157
Publisher: United States
DOI: 10.1152/ajpgi.00157.2004
PMID: 15308469
ISSN: 0193-1857
eISSN: 1522-1547
Grant note: DK-63135 / NIDDK NIH HHS DK-96001 / NIDDK NIH HHS AI-34954 / NIAID NIH HHS
Language: English
Date published: 12/2004
Academic Unit: Stead Family Department of Pediatrics; Radiation Oncology; Gastroenterology, Hepatology, Pancreatology, and Nutrition
Record Identifier: 9984047688002771

Metrics

23 Record Views

42 Times Cited - Web of Science