Nuclear localization in the biology of the CD40 receptor in normal and neoplastic human B lymphocytes.

CD40 is a tumor necrosis factor (TNF) receptor superfamily, (TNFR; TNFRSF-5) member, that initiates important signaling pathways mediating cell growth, survival, and differentiation in B-lymphocytes. Although CD40 has been extensively studied as a plasma membrane-associated growth factor receptor, we demonstrate here that CD40 is present not only in the plasma membrane and cytoplasm but also in the nucleus of normal and neoplastic B-lymphoid cells. Confocal microscopy showed that transfected CD40-green fluorescent fusion protein entered B-cell nuclei.

Structure of triglyceride-rich human low-density lipoproteins according to cryoelectron microscopy.

Low-density lipoprotein (LDL) particles from normolipidemic individuals contain a cholesteryl ester-rich core that undergoes a thermal transition from a liquid crystalline to an isotropic liquid phase between 20 and 35 degrees C. LDL from hypertriglyceridemic patients or prepared in vitro by the exchange of very low-density lipoprotein for LDL cholesteryl esters is triglyceride-rich, does not have a thermal transition above 0 degrees C, and exhibits impaired binding to the LDL receptor on normal human skin fibroblasts. Cryoelectron microscopy of LDL quick-frozen from 10 (core-frozen) and 40 degrees C (core-melted) revealed ellipsoidal particles with internal striations and round particles devoid of striations, respectively.