LBR (lamin B receptor) is a multifunctional protein that serves dual roles in cholesterol biosynthesis and nuclear membrane organization. As a sterol reductase, LBR catalyzes the reduction of the C14-unsaturated bond of lanosterol in the cholesterol biosynthesis pathway 1. The protein anchors the nuclear lamina and heterochromatin to the inner nuclear membrane, maintaining nuclear structural integrity 1. During mitosis, LBR plays a critical role in cellular energy metabolism by organizing mitosis-specific endoplasmic reticulum-mitochondrial contact sites (ERMCS), facilitating rapid calcium transport and ATP production necessary for cell division 1. LBR acts as a molecular tether, connecting the ER calcium release channel IP3R with mitochondrial VDAC2 to enable calcium influx surges that enhance ATP production during the metaphase-anaphase transition 1. In disease contexts, LBR serves as a senescence regulator, with its downregulation by microRNAs let-7b-5p and let-7c-5p contributing to chondrocyte senescence and osteoarthritis progression 2. Mutations in LBR are associated with severe developmental disorders including Greenberg dysplasia, Pelger-Huet anomaly, and Reynolds syndrome. LBR's dual function in metabolism and nuclear organization makes it essential for normal cellular homeostasis and development.