Dynein and its cofactor dynactin form a highly processive microtubule motor in the presence of an activating adaptor, such as BICD2. Different adaptors link dynein and dynactin to distinct cargoes. Here we use electron microscopy and single-molecule studies to show that adaptors can recruit a second dynein to dynactin. Whereas BICD2 is biased towards recruiting a single dynein, the adaptors BICDR1 and HOOK3 predominantly recruit two dyneins. We find that the shift towards a double dynein complex increases both the force and speed of the microtubule motor. Our 3.5 A resolution cryo-electron microscopy reconstruction of a dynein tail–dynactin–BICDR1 complex reveals how dynactin can act as a scaffold to coordinate two dyneins side-by-side. Our work provides a structural basis for understanding how diverse adaptors recruit different numbers of dyneins and regulate the motile properties of the dynein–dynactin transport machine. Cryo-electron microscopy and single-molecule studies reveal that the adaptors BICDR1 and HOOK3 recruit two dynein molecules to dynactin and thereby increase the force and speed of the dynein–dynactin microtubule motor. In eukaryotic cells, the cytoplasmic protein dynein-1 (dynein) is the main transporter of cargoes towards the minus ends of microtubules—tube-like components of the cytoskeleton that, together with motor proteins, move material within the cell. Dynein is converted into a highly processive motor protein through binding both to its cofactor dynactin and to a cargo adaptor, such as BICD2, BICDR1 or HOOK3. BICD2 preferentially binds to one molecule of dynein and one molecule of dynactin. Using cryo-electron microscopy Andrew Carter and team show that, in contrast, BICDR1 and HOOK3 bind to a complex of two dyneins, which are brought together by a dynactin scaffold. The authors' single-molecule studies highlight that this configuration increases both the force and speed of the motor complex.

/pdf/cryo-em-shows-how-dynactin-recruits-two-dyneins-for-faster-skmhzmmu3w.pdf

Cryo-EM shows how dynactin recruits two dyneins for faster movement.

Lysosome trafficking and signaling in health and neurodegenerative diseases.

Autophagy is the main homeostatic pathway guiding cytosolic materials for degradation by the lysosome. Maturation of autophagosomes requires their transport towards the perinuclear region of the cell, with key factors underlying both processes still poorly understood. Here we show that transport and positioning of late autophagosomes depends on cholesterol by way of the cholesterol-sensing Rab7 effector ORP1L. ORP1L localizes to late autophagosomes and-under low-cholesterol conditions-contacts the ER protein VAP-A, forming ER-autophagosome contact sites, which prevent minus-end transport by the Rab7-RILP-dynein complex. ORP1L-mediated contact sites also inhibit localization of PLEKHM1 to Rab7. PLEKHM1, together with RILP, then recruits the homotypic fusion and vacuole protein-sorting (HOPS) complex for fusion of autophagosomes with late endosomes and lysosomes. Thus, ORP1L, via its liganding by lipids and the formation of contacts between autophagic vacuoles and the ER, governs the last steps in autophagy that lead to the lysosomal degradation of cytosolic material.

/pdf/cholesterol-and-orp1l-mediated-er-contact-sites-control-4cxew6iq3u.pdf

Cholesterol and ORP1L-mediated ER contact sites control autophagosome transport and fusion with the endocytic pathway

Lysosomes are highly dynamic organelles that can move rapidly throughout the cell. They distribute in a rather immobile pool located around the microtubule-organizing center in a "cloud," and a highly dynamic pool in the cell periphery. Their spatiotemporal characteristics allow them to carry out multiple biological functions, such as cargo degradation, antigen presentation and plasma membrane repair. Therefore, it is not surprising that lysosomal dysfunction underlies various diseases, including cancer, neurodegenerative and autoimmune diseases. In most of these biological events, the involvement of lysosomes is dependent on their ability to move throughout the cytoplasm, to find and fuse to the correct compartments to receive and deliver substrates for further handling. These dynamics are orchestrated by motor proteins moving along cytoskeletal components. The complexity of the mechanisms responsible for controlling lysosomal transport has recently been appreciated and has yielded novel insights into interorganellar communication, as well as lipid-protein interplay. In this review, we discuss the current understanding of the mechanisms of lysosomal transport and the molecular machineries that control this mobility.

https://scholarlypublications.universiteitleiden.nl/access/item%3A3005827/view

Mechanisms of lysosomal positioning and movement.

It has been unclear how the relatively weak dynein motor can counterbalance kinesin forces during microtubule-dependent transport. Belyy et al. find that binding of dynactin and BICD2 increases the strength of the dynein motor.

Shampa Singh

Papers

Dynein Clusters into Lipid Microdomains on Phagosomes to Drive Rapid Transport toward Lysosomes.