Light-Induced Dimerization Approaches to Control Cellular Processes.

Light-inducible approaches provide a means to control biological systems with spatial and temporal resolution that is unmatched by traditional genetic perturbations. Recent developments of optogenetic and chemo-optogenetic systems for induced proximity in cells facilitate rapid and reversible manipulation of highly dynamic cellular processes and have become valuable tools in diverse biological applications. New expansions of the toolbox facilitate control of signal transduction, genome editing, "painting" patterns of active molecules onto cellular membranes, and light-induced cell cycle control. A combination of light- and chemically induced dimerization approaches have also seen interesting progress. Herein, an overview of optogenetic systems and emerging chemo-optogenetic systems is provided, and recent applications in tackling complex biological problems are discussed.

The cholesterol transfer protein GRAMD1A regulates autophagosome biogenesis.

Autophagy mediates the degradation of damaged proteins, organelles and pathogens, and plays a key role in health and disease. Thus, the identification of new mechanisms involved in the regulation of autophagy is of major interest. In particular, little is known about the role of lipids and lipid-binding proteins in the early steps of autophagosome biogenesis. Using target-agnostic, high-content, image-based identification of indicative phenotypic changes induced by small molecules, we have identified autogramins as a new class of autophagy inhibitor. Autogramins selectively target the recently discovered cholesterol transfer protein GRAM domain-containing protein 1A (GRAMD1A, which had not previously been implicated in autophagy), and directly compete with cholesterol binding to the GRAMD1A StART domain. GRAMD1A accumulates at sites of autophagosome initiation, affects cholesterol distribution in response to starvation and is required for autophagosome biogenesis. These findings identify a new biological function of GRAMD1A and a new role for cholesterol in autophagy.

Chemically induced dimerization: reversible and spatiotemporal control of protein function in cells.

Small-molecule perturbation of biological systems is able to tackle biological problems that are not accessible by classical genetic interference methods. Chemically induced dimerization (CID) has been used as a valuable tool to study various biological processes. Recent years have seen tremendous progress in the development of orthogonal and reversible CID systems. These new systems allow control over protein function with unprecedented precision and spatiotemporal resolution. While the primary application of CID has been on dissecting signal transductions, new emerging approaches have extended the scope of this technique to elucidating membrane and protein trafficking.