NOVEL MEMBERS OF THE LOW-DENSITY-LIPOPROTEIN RECEPTOR SUPERFAMILY ANDTHEIR POTENTIAL ROLES IN LIPID-METABOLISM

The list of LDL receptor superfamily relatives is still growing. The t wo most recently discovered family branches are (1) a set of receptors characterized by expression in brain and a very close relationship to the LDL and VLDL receptors, and (2) highly cross-species (man, mouse, rabbit, chicken) conserved complex mosaic receptors which contain str uctural domains so far not found in the superfamily. At present, we kn ow very little about the physiological function(s) of these molecules. They can be safely assumed, based on the presence of seven, eight or 11 clustered LDL receptor ligand binding repeats, to recognize mammali an apolipoprotein E but, based on the absence of apolipoprotein E in b irds, they may exhibit interactions quite different from and/or in add ition to typical lipoprotein receptors in vivo.