Studies on Renin Activation and Prorenin Receptor

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To clarify the possible conversion of prorenin in renin granules where conversion reportedly occurred, we investigated whether the renin granule fraction of the kidney could activate or process prorenin to the active form.Renin granules were isolated from the dog kidney cortex by discontinuous sucrose density gradient centrifugation. Inactive renin from human amniotic fluid was incubated with the subcellular fraction of the dog kidney cortex. Human active renin was quantified by immunoradiometric assay. [35S]-prorenin which was expressed by COS cell using human renin cDNA was used as a substrate for processing. [35S]-prorenin was incubated with renin granule fraction. Processing of renin was estimated by change of molecular size using SDS-polyacrylamide gel electrophoresis.The renin granule fraction that showed the highest renin activity stimulated the inactive renin to become the active form. The membrane preparation retained the activity of renin activation. Other subcellular fractions showed less renin activation. The optimal pH for renin activation by the membrane was pH 5 to 6. The activation was inhibited by N-ethylmaleimide but not by EDTA or serine protease inhibitors.In addition, [35S]-prorenin incubated with renin granule membrane revealed the conversion of prorenin to active form by estimation of the change of molecular size. This conversion was inhibited by leupeptin,N-ethylamide but not by EDTA or serine protease inhibitors.These results suggest that renin is processed by a membrane bound protease in renin granules.