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Vasopressin V2-Receptor Mobile Fraction and Ligand-Dependent Adenylate Cyclase Activity Are Directly Correlated in LLC-PK1 Renal Epithelial Cells

David A. Jans, Reiner Peters, Patricia Jans and Falk Fahrenholz
The Journal of Cell Biology
Vol. 114, No. 1 (Jul., 1991), pp. 53-60
Stable URL: http://www.jstor.org/stable/1614573
Page Count: 8
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Vasopressin V2-Receptor Mobile Fraction and Ligand-Dependent Adenylate Cyclase Activity Are Directly Correlated in LLC-PK1 Renal Epithelial Cells
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Abstract

The role of hormone receptor lateral mobility in signal transduction was studied using a cellular system in which the receptor mobile fraction could be reversibly modulated to largely varying extents. The G-protein-coupled vasopressin V2-type receptor was labeled in LLC-PK1 renal epithelial cells using a fluorescent analogue of vasopressin, and receptor lateral mobility measured using fluorescence microphotolysis (fluorescence photobleaching recovery). The receptor mobile fraction (f) was ∼0.9 at 37°C and <0.1 at 10°C, in accordance with previous studies. When cells were incubated for 1 h at 4°C without hormone, and then warmed up to 37°C and labeled with the vasopressin analogue, f increased from ∼0.4 to 0.8 over ∼1 h. The apparent lateral diffusion coefficient was not markedly affected by temperature pretreatment. Studies with radiolabeled vasopressin indicated that temperature pretreatment influenced neither receptor number nor binding/internalization kinetics. F-actin staining revealed that temperature change resulted in reversible changes of cytoskeletal structure. The maximal rate of in vivo cAMP production at 37°C in response to vasopressin, but not to forskolin (receptor-independent agonist), was also markedly influenced by preincubation of cells at 4°C, thus paralleling the effects of temperature preincubation on f. A linear correlation between f and maximal cAMP production was observed, suggesting that the receptor mobile fraction is a key parameter in hormone signal transduction in vivo. We conclude that mobile receptors are required to activate G-proteins, and discuss the implications of this for signal transduction mechanisms.

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