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Unique function of Kinesin Kif5A in localization of mitochondria in axons

Philip D Campbell1, Kimberle Shen2, Matthew R Sapio3

  • 1Departments of Developmental and Molecular Biology, and.

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience
|October 31, 2014
PubMed

Insights

Kinesin-1 (Kif5Aa) mutations cause axonal degeneration and neuropathy in zebrafish, revealing its specific role in mitochondrial transport essential for nerve maintenance, unlike redundant Kif5 family members.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Genetics

Background:

  • Kinesin proteins (Kifs) are crucial for intracellular transport, with mutations linked to neurological disorders.
  • The specific functions and redundancy of vertebrate Kinesin-1 heavy-chain family members, particularly Kif5A, in axonal health remain unclear.
  • Kif5A is implicated in Charcot-Marie-Tooth disease (CMT) and Hereditary Spastic Paraplegia (HSP), but the underlying mechanisms of axonal degeneration are poorly understood.

Purpose of the Study:

  • To investigate the specific functions of Kinesin-1 heavy-chain family members in zebrafish peripheral nervous system development and maintenance.
  • To elucidate the mechanism by which Kif5Aa contributes to axonal integrity and mitochondrial transport.
  • To understand the interplay between Kif5Aa and other kinesins or adaptors in preventing axonal degeneration.

Main Methods:

  • Generation and analysis of zebrafish kif5Aa mutants.
  • Assessment of neuronal excitability, peripheral polyneuropathy, and axonal degeneration.
  • Cell-autonomous rescue experiments using Kif5Aa and chimeric motors.
  • Investigating the role of Kinesin-3 (kif1b) and its adaptor (kbp) in exacerbating degeneration.

Main Results:

  • Zebrafish kif5Aa mutants display hyperexcitability, peripheral polyneuropathy, and axonal degeneration similar to CMT and HSP.
  • Kif5Aa mutant peripheral sensory axons exhibit a complete lack of mitochondria and subsequent degeneration, despite the presence of other Kif5 family members.
  • Kif5Aa's function in axonal maintenance is cell-autonomous and dependent on its C-terminal tail.
  • Loss of kif1b or kbp exacerbates axonal degeneration through a shared non-mitochondrial cargo pathway with Kif5Aa.

Conclusions:

  • Kif5Aa plays a critical, non-redundant role in mitochondrial transport and axonal maintenance in peripheral sensory neurons.
  • The C-terminal tail of Kif5Aa is essential for its specific function in mediating axonal integrity.
  • Kinesin-1 complexity involves specific adaptor binding and cargo transport, highlighting determinants for axonal health.
  • These findings provide insights into the pathogenesis of Kif5A-related neurological diseases like CMT and HSP.
Keywords:
CMTHSPKinesinaxon degenerationmitochondriasensory neuron

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