# Molecular mechanism of bidirectional transport

> **NIH NIH R35** · PENNSYLVANIA STATE UNIVERSITY, THE · 2021 · $815,493

## Abstract

PROJECT SUMMARY
Bidirectional transport of vesicles and organelles in cells involves a tug-of-war between the microtubule motors
kinesin and dynein. This transport is particularly important in the axons and dendrites of neurons and in cilia and
flagella, and transport defects are linked to neurodegenerative diseases such as Alzheimer’s and ALS, as well
as ciliopathies. Although many of the molecular players are known, the working mechanisms of these component
parts and how their activities combine to achieve the emergent property of bidirectional transport are not
sufficiently understood. The goal of this proposal is to bridge the gulf in understanding between the
mechanochemistry of single kinesin and dynein motors and the bidirectional transport dynamics of vesicles and
organelles observed in cells. Unresolved questions include: How does load affect the mechanochemistry and
detachment kinetics of different kinesins and dynein? How do opposing motors coordinate and compete to
achieve bidirectional transport? How do regulatory proteins, microtubule associated proteins and tubulin post-
translational modifications alter the balance of plus- and minus-end directed motility to achieve proper vectorial
transport? To address these questions, Interferometric Scattering (iSCAT) microscopy with nanometer spatial
precision and millisecond temporal resolution will be used to track individual motor domains, single motor
proteins, and multi-motor assemblies as they step along their microtubule tracks. These microscopy studies will
be complemented by stopped-flow kinetics investigations, in vitro reconstitution experiments, and computational
modeling to understand assemblies of increasing complexity. Specific motor mechanisms to be investigated
include the origin of the fast speed and superprocessivity of kinesin-3, the polymerase mechanism of kinesin-5,
and the molecular basis of dynein activation by its adapter proteins. A DNA tensiometer will be developed to
understand the influence of mechanical load on kinesin and dynein mechanochemistry, and statistical tools will
be developed to extract load-dependent detachment kinetics from these experiments. Finally, multi-motor
assemblies will be built using DNA origami, which allows for precise control of motor number and positioning,
and reconstituted lipid vesicles, which mimic the mechanical and diffusional properties of intracellular cargo. This
work will advance our understanding of how organelles are correctly positioned in cells and how specific
intracellular cargo are reliably targeted to their proper cellular locations.

## Key facts

- **NIH application ID:** 10086235
- **Project number:** 1R35GM139568-01
- **Recipient organization:** PENNSYLVANIA STATE UNIVERSITY, THE
- **Principal Investigator:** William Olaf Hancock
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $815,493
- **Award type:** 1
- **Project period:** 2021-03-01 → 2026-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10086235

## Citation

> US National Institutes of Health, RePORTER application 10086235, Molecular mechanism of bidirectional transport (1R35GM139568-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10086235. Licensed CC0.

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