Myosin-Vb functions as a dynamic tether for peripheral endocytic compartments during transferrin trafficking.
BACKGROUND
Myosin-Vb has been shown to be involved in the recycling of diverse proteins in multiple cell types. Studies on transferrin trafficking in HeLa cells using a dominant-negative myosin-Vb tail fragment suggested that myosin-Vb was required for recycling from perinuclear compartments to the plasma membrane. However, chemical-genetic, dominant-negative experiments, in which myosin-Vb was specifically induced to bind to actin, suggested that the initial hypothesis was incorrect both in its site and mode of myosin-Vb action. Instead, the chemical-genetic data suggested that myosin-Vb functions in the actin-rich periphery as a dynamic tether on peripheral endosomes, retarding transferrin transport to perinuclear compartments.


RESULTS
In this study, we employed both approaches, with the addition of overexpression of full-length wild-type myosin-Vb and switching the order of myosin-Vb inhibition and transferrin loading, to distinguish between these hypotheses. Overexpression of full-length myosin-Vb produced large peripheral endosomes. Chemical-genetic inhibition of myosin-Vb after loading with transferrin did not prevent movement of transferrin from perinuclear compartments; however, virtually all myosin-Vb-decorated particles, including those moving on microtubules, were halted by the inhibition. Overexpression of the myosin-Vb tail caused a less-peripheral distribution of early endosome antigen-1 (EEA1).


CONCLUSIONS
All results favored the peripheral dynamic tethering hypothesis.
Provance
D William
DW
McLaughlin Research Institute, Great Falls, MT, USA. billp@mri.montana.edu
Addison
Erin J
EJ
Wood
Patrick R
PR
Chen
David Z
DZ
Silan
Colleen M
CM
Mercer
John A
JA
D001692:Biological Transport; D002451:Cell Compartmentation; D011992:Endosomes / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D024701:Myosin Type V / Q000378:metabolism*; D014162:Transfection; D014168:Transferrin / Q000378:metabolism*
D014168:Transferrin; D049452:Green Fluorescent Proteins; D024701:Myosin Type V