Cooperation between microtubule- and actin-based motor proteins

Area of Science:

• Cell Biology
• Molecular Motors
• Cytoskeletal Dynamics

Background:

• Organelle transport is crucial for cellular function, often modeled as a two-step process involving microtubule-based long-range movement and actin-based local delivery.
• Class V myosins are implicated as key actin-based motors in various cell types, including neurons and pigment cells.
• Genetic studies in mice (dilute) and yeast (myo2) have highlighted the role of class V myosins in organelle transport, with yeast studies suggesting a supporting role for the kinesin-related protein Smy1p.

Purpose of the Study:

• To investigate the relationship between actin-based motors (class V myosins) and microtubule-based motors (kinesins) in organelle transport.
• To explore potential physical interactions between these distinct motor protein superfamilies.

Main Methods:

• Analysis of genetic mutations affecting organelle transport in model organisms (mice and yeast).
• Investigating genetic interactions between myosin and kinesin-related proteins.
• Biochemical or cellular assays to detect physical interactions between motor proteins.

Main Results:

• Evidence supports a model where class V myosins mediate local organelle delivery after long-range transport.
• Mutations in class V myosins (dilute in mice, myo2 in yeast) impair organelle transport.
• Genetic interactions in yeast suggest a supporting role for Smy1p (kinesin-related protein) in myosin-driven transport.
• Crucially, direct physical interaction between class V myosins and kinesin or Smy1p has been observed in both mice and yeast.

Conclusions:

• Class V myosins and kinesins are not only functionally linked but also physically interact, suggesting a coordinated mechanism for organelle transport.
• This interaction bridges the microtubule and actin cytoskeletal systems, providing a more integrated understanding of intracellular transport.
• The findings reveal a novel cross-talk between different motor protein families, impacting fundamental cellular processes.