SREBP is a membrane-bound transcription factor that is released and activated by proteases in response to low cellular cholesterol levels. The cleaved SREBP acts as a transcription factor to increase the synthesis of low-density lipoprotein (LDL) receptor, cholesterol-biosynthetic enzymes, and enzymes of fatty acid synthesis. Goldstein, Brown, and colleagues produced truncated forms of SREBP containing only the portion responsible for transcriptional activation and found that cultured cells expressing this protein filled up with large amounts of cholesteryl esters. buy asthma inhaler
In theca cells, the activation of caspase-3 and cleavage of SREBP might account for the hypertrophy and accumulation of lipid droplets observed after gonadotropin withdrawal with the anti-eCG antiserum. It is possible that lipid droplets full of esterified cholesterol could serve to allow the theca to continue to produce large amounts of androgens to induce or augment apoptosis in the granulosa cells during follicular atresia. The present studies have not demonstrated that caspase-3 was activated during apoptosis.