Intramembrane proteolysis of sterol-regulatory element-binding proteins (SREBPs) within the first transmembrane segment thereby releasing the N-terminal segment with a portion of the transmembrane segment attached. Site-2 cleavage comes after site-1 cleavage which takes place in the lumenal loop.
Expressed in heart, brain, placenta, lung, liver, muscle, kidney and pancreas.
Involvement in disease
Defects in MBTPS2 are the cause of ichthyosis follicularis-atrichia-photophobia syndrome (IFAPS) [MIM:308205]. A syndrome characterized by a peculiar triad of follicular ichthyosis, total or subtotal atrichia, and photophobia of varying degree. Histopathologically, the epidermal granular layer is generally well-preserved or thickened at the infundibulum. Hair follicles are poorly developed and tend to be surrounded by an inflammatory infiltrate. A subgroup of patients is described with lamellar rather than follicular ichthyosis. Non-consistent features may include growth and psychomotor retardation, aganglionic megacolon, seizures and nail dystrophy. Defects in MBTPS2 are a cause of keratosis follicularis spinulosa decalvans X-linked (KFSDX) [MIM:308800]. A rare disorder affecting the skin and the eye. Affected men show thickening of the skin of the neck, ears, and extremities, especially the palms and soles, loss of eyebrows, eyelashes and beard, thickening of the eyelids with blepharitis and ectropion, and corneal degeneration.