Current Opinion in Lipidology · 1992 · 86 citations · 0 references
Life SciencesBiochemistryMolecular BiologyInnate ImmunityLipid BiochemistryMembrane BiochemistryCell Membrane StructureLipid-protein InteractionsMembrane DomainsMembrane Lipid CompositionMembrane ProteinsProtein-lipid InteractionsApolipoprotein FunctionComplement System ActivationElectrophoretic MobilityLipid-binding DomainsMembrane Binding DomainsPlasma Membrane Lipid CompositionProtein Binding DomainsTransport Across Cell Membranes
Apolipoprotein (apo)J is unique among secreted lipid transport proteins with structural features in common both with other apolipoproteins and with components of the complement system. Its two disulfide-linked subunits are produced by post-translational cleavage of a single polypeptide chain. Moreover, apoj is present in distinct subclasses of high and very-high-density plasma lipoproteins which have aα electrophoretic mobility. We propose that apoj acts in both surface-bound and diffusible forms to maintain cell membrane integrity by using its hydrophobic-binding domains to police the membrane and extracellular space against potentially harmful hydrophobic molecules. This hypothesis is founded on the restriction of apoj gene expression to specific cell types, its known lipid-binding capacity, its association with cell membranes, its capacity to inhibit the membrane attack complement complex, and its marked induction in degenerative situations.