SREBP and Cellular Cholesterol Metabolism How cells use
cholesterol is important in terms of influencing LDL levels in
your blood. Study Title:Sterol Regulatory Element-binding
Proteins (SREBPs): Key Regulators of Nutritional Homeostasis and
Insulin Action* The sterol regulatory element-binding proteins
(SREBPs)1 were first identified by two groups working
independently on cholesterol metabolism (1, 2) and fat cell
differentiation (3). Subsequent studies have demonstrated there
are three major SREBP isoforms encoded by two different genes
(4). These unique members of the basic helix-loop-helix leucine
zipper (bHLHLZ) family of transcriptional regulatory proteins
can be distinguished from other family members by two
characteristics. The first is they are synthesized as precursors
that are threaded into membranes of the endoplasmic reticulum
and nuclear envelope in a hairpin orientation such that the
amino and carboxyl tails both face the cytoplasm. The amino-
terminal half of the precursor is clipped out of the