Apical enrichment of human EGF precursor in Madin-Darby canine kidney cells involves preferential basolateral ectodomain cleavage sensitive to a metalloprotease inhibitor.

Dempsey PJ, Meise KS, Yoshitake Y, Nishikawa K, Coffey RJ
J Cell Biol. 1997 138 (4): 747-58

PMID: 9265643 · PMCID: PMC2138042 · DOI:10.1083/jcb.138.4.747

EGF precursor (proEGF) is a member of the family of membrane-anchored EGF-like growth factors that bind with high affinity to the epidermal growth factor receptor (EGFR). In contrast to human transforming growth factor-alpha precursor (proTGFalpha), which is sorted basolaterally in Madin-Darby canine kidney (MDCK) cells (Dempsey, P., and R. Coffey, 1994. J. Biol. Chem. 269:16878-16889), we now demonstrate that human proEGF overexpressed in MDCK cells is found predominantly at the apical membrane domain under steady-state conditions. Nascent proEGF (185 kD) is not sorted but is delivered equally to the apical and basolateral membranes, where it is proteolytically cleaved within its ectodomain to release a soluble 170-kD EGF form into the medium. Unlike the fate of TGFalpha in MDCK cells, the soluble 170-kD EGF species accumulates in the medium, does not interact with the EGFR, and is not processed to the mature 6-kD peptide. We show that the rate of ectodomain cleavage of 185-kD proEGF is fourfold greater at the basolateral surface than at the apical surface and is sensitive to a metalloprotease inhibitor, batimastat. Batimastat dramatically inhibited the release of soluble 170-kD EGF into the apical and basal medium by 7 and 60%, respectively, and caused a concordant increase in the expression of 185-kD proEGF at the apical and basolateral cell surfaces of 150 and 280%, respectively. We propose that preferential ectodomain cleavage at the basolateral surface contributes to apical domain localization of 185-kD proEGF in MDCK cells, and this provides a novel mechanism to achieve a polarized distribution of cell surface membrane proteins under steady-state conditions. In addition, differences in disposition of EGF and TGFalpha in polarized epithelial cells offer a new conceptual framework to consider the actions of these polypeptide growth factors.

MeSH Terms (19)

Animals Biological Transport Cell Line Cell Membrane Cell Polarity Dogs Epidermal Growth Factor Extracellular Space Humans Hydrolysis Kidney Metalloendopeptidases Molecular Weight Phenylalanine Protein Precursors Protein Processing, Post-Translational Protein Structure, Tertiary Solubility Thiophenes

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