An induced extracellular matrix protein reverses the polarity of band 3 in intercalated epithelial cells.
The intercalated epithelial cell exists in two interconvertible forms in vivo, one where band 3 protein is apical and the other where it is basolateral. We seeded an immortalized clone of these cells at low density and found that band 3 was apical at confluence. There was little or no apical endocytosis. But when the cells were plated at high density, band 3 was basolateral, and there was vigorous apical endocytosis. Extracellular matrix produced by high density cells was able to retarget band 3 in low density cells and to induce apical endocytosis, as did a 230 kd protein partially purified from this matrix. Therefore, polarized targeting of some proteins is determined by external cues that might determine their polarity by reorganizing the cytoplasm.
van Adelsberg
J
J
Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York 10032.
Edwards
J C
JC
Takito
J
J
Kiss
B
B
al-Awqati
Q
Q
D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000502:physiology*; D017920:Antiporters / Q000502:physiology*; D002452:Cell Count; D016764:Cell Polarity / Q000502:physiology*; D027963:Chloride-Bicarbonate Antiporters; D002999:Clone Cells; D004705:Endocytosis / Q000502:physiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000166:cytology; D011817:Rabbits
D001457:Anion Exchange Protein 1, Erythrocyte; D017920:Antiporters; D027963:Chloride-Bicarbonate Antiporters; D016326:Extracellular Matrix Proteins