Tuning microtubule-based transport through filamentous MAPs: the problem of dynein.
We recently proposed that regulating the single-to-multiple motor transition was a likely strategy for regulating kinesin-based transport in vivo. In this study, we use an in vitro bead assay coupled with an optical trap to investigate how this proposed regulatory mechanism affects dynein-based transport. We show that tau's regulation of kinesin function can proceed without interfering with dynein-based transport. Surprisingly, at extremely high tau levels--where kinesin cannot bind microtubules (MTs)--dynein can still contact MTs. The difference between tau's effects on kinesin- and dynein-based motility suggests that tau can be used to tune relative amounts of plus-end and minus-end-directed transport. As in the case of kinesin, we find that the 3RS isoform of tau is a more potent inhibitor of dynein binding to MTs. We show that this isoform-specific effect is not because of steric interference of tau's projection domains but rather because of tau's interactions with the motor at the MT surface. Nonetheless, we do observe a modest steric interference effect of tau away from the MT and discuss the potential implications of this for molecular motor structure.
Vershinin
Michael
M
Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697, USA.
Xu
Jing
J
Razafsky
David S
DS
King
Stephen J
SJ
Gross
Steven P
SP
D001692:Biological Transport; D002021:Buffers; D004398:Dyneins / Q000737:chemistry / Q000502:physiology*; D016547:Kinesins / Q000502:physiology; D008863:Microspheres; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D008870:Microtubules / Q000502:physiology*; D011137:Polystyrenes / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013205:Staphylococcal Protein A / Q000378:metabolism; D014404:Tubulin / Q000302:isolation & purification; D016875:tau Proteins / Q000302:isolation & purification / Q000502:physiology
D002021:Buffers; D008869:Microtubule-Associated Proteins; D011137:Polystyrenes; D013205:Staphylococcal Protein A; D014404:Tubulin; D016875:tau Proteins; D004398:Dyneins; D016547:Kinesins