Microsomal triglyceride transfer protein

The microsomal triglyceride transfer protein (MTP) is a protein complex of two proteins that is localized in the endoplasmic reticulum of all mammals.

MTP catalyzes the transport and incorporation of triglycerides, cholesterol esters, phospholipids and retinyl palmitate (vitamin A) into the plasma lipoproteins associated with apolipoprotein B (Apo B) (VLDL, IDL, LDL, chylomicrons). MTP also participates in the recycling of the antigen-presenting glycoprotein CD1d in the lysosomes. In humans, MTP is mainly expressed in the liver and small intestine. In the intestinal cells, the formation of MTP is stimulated by cholesterol, but slowed down by insulin. Another signalling pathway that influences MP expression seems to be via the hormones leptin and melanocortin.

Autosomal recessive mutations in the MTP gene (4q22-q24), which codes for the large subunit of the MTT complex, can lead to MTP deficiency and to hypo- or abetalipoproteinemia (see below Familial hypobetalipoproteinemia).