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Inhibition of Na + ‐H + exchanger‐3 interferes with apical receptor‐mediated endocytosis via vesicle fusion
Author(s) -
Gekle Michael,
Freudinger Ruth,
Mildenberger Sigrid
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0619h.x
Subject(s) - endocytosis , endocytic cycle , microbiology and biotechnology , exocytosis , endosome , bulk endocytosis , receptor mediated endocytosis , vesicle , vesicle fusion , chemistry , biology , biochemistry , receptor , secretion , membrane , intracellular , synaptic vesicle
1 Receptor‐mediated endocytosis in epithelial cells is a crucial mechanism for transport of macromolecules and regulation of cell‐surface protein expression. Na + ‐H + exchanger type 3 (NHE3) has been shown to cycle between the apical plasma membrane and the early endosomal compartment and to interfere with endocytosis. 2 In the present study we investigated in detail the NHE3‐dependent step of apical endocytosis in an epithelial cell line (opossum kidney cells). 3 Inhibition of NHE3 led to a rapid dose‐dependent inhibition of apical albumin endocytosis but did not affect basolateral transferrin endocytosis. Re‐exocytosis of albumin was not increased by NHE3 inhibition. 4 NHE3 dependency of albumin endocytosis was still observed at 20 °C or when microtubules had been disrupted. This was not the case for inhibition of vacuolar H + ‐ATPase. 5 NHE3 inhibition rapidly blocked internalisation of pre‐bound albumin and attenuated degradation of internalised albumin without changing general protein degradation. 6 Furthermore, NHE3 inhibition reduced the rate of endocytic vesicle fusion significantly. 7 In summary, our data indicate that NHE3 is important for the early phase of the apical endocytic pathway, located between the plasma membrane and early endosomes, at least in part due to its involvement in endocytic vesicle fusion.