A molecular toolbox for interrogation of membrane contact sites

Membrane contact sites (MCSs) are specialized subcellular compartments formed by closely apposed membranes from two organelles. The intermembrane gap is separated by a distance ranging from 10 to 35 nm. MCSs are typically maintained through dynamic protein–protein and protein–lipid interactions. These intermembrane contact sites constitute important intracellular signalling hotspots to mediate a plethora of cellular processes, including calcium homeostasis, lipid metabolism, membrane biogenesis and organelle remodelling. In recent years, a series of genetically encoded probes and chemogenetic or optogenetic actuators have been invented to aid the visualization and interrogation of MCSs in both fixed and living cells. These molecular tools have greatly accelerated the pace of mechanistic dissection of membrane contact sites at the molecular level. In this review, we present an overview on the latest progress in this endeavour, and provide a general guide to the selection of methods and molecular tools for probing interorganellar membrane contact sites. Schematic diagram showing the interorganellar membrane contact sites (MCSs), which are intimately involved in the regulation of lipid and ion exchange, organelle biogenesis and subcellular positioning. Innovative methods and genetically encoded molecular tools have been developed to aid the visualization of MCSs and non‐invasive manipulation of interorganellar communication with high spatiotemporal precision.