Cooperation between microtubule- and actin-based motor proteins.

Organelle transport has been proposed to proceed in two steps: long-range transport along microtubules and local delivery via actin filaments. This model is supported by recent studies of pigment transport in several cell types and transport in neurons, and in several cases, class V myosin has been implicated as the actin-based motor. Mutations in mice (dilute) and yeast (myo2) have also implicated this class of myosin in organelle transport, and genetic interactions in yeast have indicated that a kinesin-related protein (Smy1p) plays a supporting role. This link between members of two different motor superfamilies has now taken a surprising turn: There is evidence for a physical interaction between class V myosins and kinesin or Smy1p in both mice and yeast.