Lipoprotein Particles Interact with Membranes and Transfer Their Cargo without Receptors

Lipid transfer from lipoprotein particles to cells is essential for lipid homeostasis. High density lipoprotein (HDL) particles are mainly captured by cell-membrane-associated scavenger receptor class B type 1 (SR-B1) from the blood stream while low and very low density lipoprotein (LDL, VLDL) particles are mostly taken up by receptor-mediated endocytosis. However, the role of the target lipid membrane itself in the transfer process has been largely neglected so far. Here, we study how lipoprotein particles (HDL, LDL and VLDL) interact with synthetic lipid bilayers and cell-derived membranes and transfer their cargo subsequently. Employing cryo-electron microscopy, spectral imaging and fluorescence (cross) correlation spectroscopy allowed us to observe integration of all major types of lipoprotein particles into the membrane and delivery of their cargo in a receptor-independent manner. Importantly, biophysical properties of the target cell membranes change upon cargo delivery. The concept of receptor-independent interaction of lipoprotein particles with membranes helps to better understand lipoprotein particle biology and can be exploited for novel treatments of dyslipidemia diseases.