Lateral mobility of the vasopressin renal-type V2-receptor was investigated in LLC-PK1, porcine epithelial cells using the technique of fluorescence microphotolysis (photobleaching) and a rhodamine-labelled vasopressin analogue. At various times after ligand addition, cells were analyzed for both receptor lateral mobility and ligand internalization. The V2-receptor mobile fraction diminished from 0.9 to 0.43 over 60 min at 37°C. whereas the apparent lateral diffusion coefficient remained essentially unchanged (2-3 × 10-10 cm2 s). Interestingly, the fraction of immobile V2-receptors corresponded exactly with the fraction of internalized receptors, implying a functional relationship. These observations together with comparable results reported for other polypeptide hormone receptors indicate a possible machanistic role for receptor immobilization in the desensitization of hormonal response.
- Lateral mobility
- Vasopressin renal V-type receptor: Photobleaching