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Updated: Mar 30, 2026
Characterizing the Composition of Molecular Motors on Moving Axonal Cargo Using "Cargo Mapping" Analysis
Published on: October 30, 2014
Dynamic microtubule organization and mitochondrial transport are regulated by distinct Kinesin-1 pathways
Anna Melkov1, Yasmin Simchoni1, Yehonatan Alcalay1
1Department of Life Sciences, Ben-Gurion University, Beer-Sheva 8410500, Israel.
Abstract:
The microtubule (MT) plus-end motor kinesin heavy chain (Khc) is well known for its role in long distance cargo transport. Recent evidence showed that Khc is also required for the organization of the cellular MT network by mediating MT sliding. We found that mutations in Khc and the gene of its adaptor protein, kinesin light chain (Klc) resulted in identical bristle morphology defects, with the upper part of the bristle being thinner and flatter than normal and failing to taper towards the bristle tip. We demonstrate that bristle mitochondria transport requires Khc but not Klc as a competing force to dynein heavy chain (Dhc). Surprisingly, we demonstrate for the first time that Dhc is the primary motor for both anterograde and retrograde fast mitochondria transport. We found that the upper part of Khc and Klc mutant bristles lacked stable MTs. When following dynamic MT polymerization via the use of GFP-tagged end-binding protein 1 (EB1), it was noted that at Khc and Klc mutant bristle tips, dynamic MTs significantly deviated from the bristle parallel growth axis, relative to wild-type bristles. We also observed that GFP-EB1 failed to concentrate as a focus at the tip of Khc and Klc mutant bristles. We propose that the failure of bristle tapering is due to defects in directing dynamic MTs at the growing tip. Thus, we reveal a new function for Khc and Klc in directing dynamic MTs during polarized cell growth. Moreover, we also demonstrate a novel mode of coordination in mitochondrial transport between Khc and Dhc.
Insights
Kinesin heavy chain (Khc) and kinesin light chain (Klc) direct microtubule dynamics for polarized cell growth. Dynein heavy chain (Dhc) is the primary motor for fast mitochondria transport in both directions.
Area of Science:
- Cell Biology
- Molecular Motors
- Cytoskeletal Dynamics
Background:
- Kinesin heavy chain (Khc) is a motor protein crucial for intracellular transport and microtubule organization.
- Kinesin light chain (Klc) is an adaptor protein that works with Khc.
- Microtubule (MT) organization is essential for cellular structure and function.
Purpose of the Study:
- To investigate the roles of Khc and Klc in bristle morphology and microtubule organization.
- To elucidate the motor proteins involved in mitochondria transport within bristles.
- To understand the coordination between different motor proteins in cellular processes.
Main Methods:
- Analysis of Khc and Klc mutations in bristle morphology.
- Mitochondria transport assays in mutant bristles.
- Live imaging of dynamic microtubules using GFP-tagged end-binding protein 1 (EB1).
Main Results:
- Khc and Klc mutations cause identical bristle defects, including abnormal tapering.
- Dynein heavy chain (Dhc) is identified as the primary motor for fast anterograde and retrograde mitochondria transport.
- Mutant bristles exhibit unstable microtubules and aberrant microtubule growth direction at the tip.
- Khc and Klc are required for proper microtubule organization and dynamic MT guidance during polarized growth.
Conclusions:
- Khc and Klc play a novel role in directing dynamic microtubules during polarized cell growth, affecting bristle tapering.
- Dhc is the principal motor for fast mitochondria transport, challenging previous assumptions.
- A new mode of coordination between Khc and Dhc in mitochondria transport is revealed.
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