SREBF1 Recombinant Rabbit mAb (S-4175-21)

Sterol regulatory element-binding protein 1 (SREBF1, also known as SREBP-1) is a key transcription factor that regulates lipid metabolism in mammalian cells and belongs to the basic helix-loop-helix leucine zipper (bHLH-Zip) protein family. It exists primarily in two isoforms, SREBP-1a and SREBP-1c, which are generated from the same gene by alternative promoters. SREBP-1c is the predominant isoform in rodent and human liver and adipose tissue, where it responds to insulin signaling and regulates de novo synthesis of fatty acids and triglycerides. SREBF1 is synthesized as a precursor on the endoplasmic reticulum membrane in association with SCAP. When intracellular sterol levels are low, SCAP senses the change and escorts SREBF1 via COPII vesicles to the Golgi apparatus, where it undergoes sequential proteolytic cleavage by site-1 protease (S1P) and site-2 protease (S2P), releasing an active N-terminal fragment that translocates into the nucleus. The nuclear active form then recognizes and binds to sterol regulatory elements (SREs) or E-box sequences in the promoters of target genes, activating the transcription of a series of lipogenic enzymes including acetyl-CoA carboxylase, fatty acid synthase (FASN), and stearoyl-CoA desaturase 1 (SCD1). Insulin upregulates SREBP-1c expression indirectly through the PI3K/Akt signaling pathway and the transcription factor LXR, whereas glucagon and AMPK phosphorylation suppress its activity, thereby promoting lipid storage when energy is abundant and inhibiting lipogenesis during starvation. Aberrant hyperactivation of SREBF1 is closely associated with fatty liver disease, insulin resistance, and type 2 diabetes, making it an important potential target for the treatment of metabolic disorders.