Biology subjects

Badieyan, S.

Publications and source records attributed to Badieyan, S..

4 recordsLinked to original sources

bioRxiv2023

The Bicaudal-D/Egalitarian complex defines the specificity of cargo transport by Dynein.

Numerous motors of the Kinesin family contribute to plus-end microtubule transport. However, almost all transport towards the minus-end of microtubules involves a single motor, cytoplasmic Dynein (Dynein). To gain motility, Dynein must interact with activating cargo adaptors. One such adaptor is Bicaudal-D (BicD; BICD2 in humans). Mutations in BICD2 are associated with Spinal Muscular Atrophy (SMA), a degenerative motor neuron disease. BicD is autoinhibited from binding Dynein in the absence of cargo. A well-characterized cargo for BicD is the RNA binding protein, Egalitarian (Egl). Egl in conjunction with BicD links mRNA to Dynein in the Drosophila egg chamber and embryo. To better understand how Dynein is activated and whether BicD links additional cargo with Dynein, we defined the BicD interactome in the presence and absence of Egl. This revealed a vast number of potentially novel BicD cargos including the nucleoporin Nup358/RANBP2, a known cargo of mammalian BICD2. In strains depleted of Egl, BicD remained associated with most of its cargo including Nup358. However, the interaction of BicD with Dynein was reduced. Consequently, the localization of Nup358 and its association with Dynein was disrupted. Thus, while BicD can bind diverse cargos, linking these cargos with Dynein requires Egl. Furthermore, our studies revealed that a SMA associated mutation in the cargo binding domain of BicD enhanced the Dynein mediated localization of certain cargos but disrupted the localization of others. At the organismal level, this mutation resulted in compromised mobility. Specific transport defects might therefore underlie the etiology of BicD associated SMA.

cell biology↗

bioRxiv2023

HIV-1 binds dynein directly to hijack microtubule transport machinery

Viruses exploit host cytoskeletal elements and motor proteins for trafficking through the dense cytoplasm. Yet the molecular mechanism that describes how viruses connect to the motor machinery is unknown. Here, we demonstrate the first example of viral microtubule trafficking from purified components: HIV-1 hijacking microtubule transport machinery. We discover that HIV-1 directly binds to the retrograde microtubule-associated motor, dynein, and not via a cargo adaptor, as previously suggested. Moreover, we show that HIV-1 motility is supported by multiple, diverse dynein cargo adaptors as HIV-1 binds to dynein light and intermediate chains on dyneins tail. Further, we demonstrate that multiple dynein motors tethered to rigid cargoes, like HIV-1 capsids, display reduced motility, distinct from the behavior of multiple motors on membranous cargoes. Our results introduce a new model of viral trafficking wherein a pathogen opportunistically hijacks the microtubule transport machinery for motility, enabling multiple transport pathways through the host cytoplasm.

microbiology↗

bioRxiv2022

Kinesin-1, -2 and -3 motors use family-specific mechanochemical strategies to effectively compete with dynein during bidirectional transport

Bidirectional cargo transport in neurons requires competing activity of motors from the kinesin-1, -2 and -3 superfamilies against cytoplasmic dynein-1. Previous studies demonstrated that when kinesin-1 attached to dynein-dynactin-BicD2 (DDB) complex, the tethered motors move slowly with a slight plus-end bias, suggesting kinesin-1 overpowers DDB but DDB generates a substantial hindering load. Compared to kinesin-1, motors from the kinesin-2 and -3 families display a higher sensitivity to load in single-molecule assays and are thus predicted to be overpowered by dynein complexes in cargo transport. To test this prediction, we used a DNA scaffold to pair DDB with members of the kinesin-1, -2 and -3 families to recreate bidirectional transport in vitro, and tracked the motor pairs using two-channel TIRF microscopy. Unexpectedly, we find that when both kinesin and dynein are engaged and stepping on the microtubule, kinesin-1, -2, and -3 motors are able to effectively withstand hindering loads generated by DDB. Stochastic stepping simulations reveal that kinesin-2 and -3 motors compensate for their faster detachment rates under load with faster reattachment kinetics. The similar performance between the three kinesin transport families highlights how motor kinetics play critical roles in balancing forces between kinesin and dynein, and emphasizes the importance of motor regulation by cargo adaptors, regulatory proteins, and the microtubule track for tuning the speed and directionality of cargo transport in cells.

cell biology↗

bioRxiv2021

A kinesin-1 variant reveals motor-induced microtubule damage in cells

Kinesins drive the transport of cellular cargoes as they walk along microtubule tracks, however, recent work has suggested that the physical act of kinesins walking along microtubules can stress the microtubule lattice. Here, we describe a kinesin-1 KIF5C mutant with an increased ability to generate defects in the microtubule lattice as compared to the wild-type motor. Expression of the mutant motor in cultured cells resulted in microtubule breakage and fragmentation, suggesting that kinesin-1 variants with increased damage activity would have been selected against during evolution. The increased ability to damage microtubules is not due to the altered motility properties of the mutant motor as expression of the kinesin-3 motor KIF1A, which has similar single-motor motility properties, also caused increased microtubule pausing, bending, and buckling but not breakage. In cells, motor-induced microtubule breakage could not be prevented by increased a-tubulin K40 acetylation, a post-translational modification known to increase microtubule flexibility. In vitro, lattice damage induced by wild-type KIF5C was repaired by soluble tubulin and resulted in increased rescues and microtubule growth whereas lattice damage induced by the KIF5C mutant resulted in larger repair sites that made the microtubule vulnerable to breakage and fragmentation when under mechanical stress. These results demonstrate that kinesin-1 motility causes defects in and damage to the microtubule lattice in cells. While cells have the capacity to repair lattice damage, conditions that exceed this capacity result in microtubule breakage and fragmentation and may contribute to human disease.

cell biology↗