Hook Adaptors Induce Unidirectional Processive Motility by Enhancing the Dynein-Dynactin Interaction

Abstract

Cytoplasmic dynein drives the majority of minus end-directed vesicular and organelle motility in the cell. However, it remains unclear how dynein is spatially and temporally regulated given the variety of cargo that must be properly localized to maintain cellular function. Recent work has suggested that adaptor proteins provide a mechanism for cargo-specific regulation of motors. Of particular interest, studies in fungal systems have implicated Hook proteins in the regulation of microtubule motors. Here we investigate the role of mammalian Hook proteins, Hook1 and Hook3, as potential motor adaptors. We used optogenetic approaches to specifically recruit Hook proteins to organelles and observed rapid transport of peroxisomes to the perinuclear region of the cell. This rapid and efficient translocation of peroxisomes to microtubule minus ends indicates that mammalian Hook proteins activate dynein rather than kinesin motors. Biochemical studies indicate that Hook proteins interact with both dynein and dynactin, stabilizing the formation of a supramolecular complex. Complex formation requires the N-terminal domain of Hook proteins, which resembles the calponin-homology domain of end-binding (EB) proteins but cannot bind directly to microtubules. Single-molecule motility assays using total internal reflection fluorescence microscopy indicate that both Hook1 and Hook3 effectively activate cytoplasmic dynein, inducing longer run lengths and higher velocities than the previously characterized dynein activator bicaudal D2 (BICD2). Together, these results suggest that dynein adaptors can differentially regulate dynein to allow for organellespecific tuning of the motor for precise intracellular trafficking.Microtubules provide a polarized highway to facilitate the transport of organelles and vesicles throughout the cell. The minus ends of microtubules are usually nucleated near the cell center, with the plus ends oriented outward, toward the cell periphery. This polarity ensures that microtubule motors drive motility in a specific direction; kinesin motors generally drive plus end motility, whereas minus end traffic is primarily driven by cytoplasmic dynein. Regulation of these opposing motors is vital for cell survival, particularly in specialized cells like neurons that require efficient transport over long distances (1). However, it remains unclear how microtubule motors are spatially and temporally regulated to control the intracellular trafficking of specific cargo. As a single major form of cytoplasmic dynein drives the transport of a wide array of cargos, including endosomes, RNA granules, and mitochondria (2-4), it is likely that the transport properties of dynein are modulated by the binding of cargo-specific adaptor molecules.

Moving and positioning the endolysosomal system

“…Centripetal transport of EEs, for example, is mediated by Rab5 and the Rab5-effector FHF complex, composed of FHIP, Hook and FTS subunits [16,17,18,19,20]. FHIP is the subunit that directly interacts with Rab5 [20], whereas Hook simultaneously binds to dynein and dynactin, stabilizing this complex and enhancing the processivity of transport [21,22]. …”

Hitchhiking: A Non-Canonical Mode of Microtubule-Based Transport

“…Mammalian dynein, unlike the well-characterized S. cerevisiae dynein [65], requires dynactin and a coiled-coil cargo adaptor (or ‘activator’) to achieve processive motility [66,67]. Five activators have been confirmed so far: Bicaudal-D2 (BicD2), Hook3, Hook1, Spindly, and Rab11–FIP3 [66–68]. While some cargo adaptors serve as activators, others are involved only in recruiting dynein to its cargo [7,8].…”

miR‐496 remedies hypoxia reoxygenation–induced H9c2 cardiomyocyte apoptosis via Hook3‐targeted PI3k/Akt/mTOR signaling pathway activation

“…[11][12][13][14][15] Hooks, with their separate subcellular localizations, naturally exhibit distinct cellular functionality. [11][12][13][14][15] Hooks, with their separate subcellular localizations, naturally exhibit distinct cellular functionality.…”