Regulation of microtubule-based transport by MAP4

Microtubule (MT)-based transport of organelles driven by the opposing MT motors kinesins and dynein is tightly regulated in cells, but the underlying molecular mechanisms remain largely unknown. Here we tested the regulation of MT transport by the ubiquitous protein MAP4 using Xenopus melanophores a...

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Bibliographic Details
Published in:Molecular biology of the cell 2014-10, Vol.25 (20), p.3119-3132
Main Authors: Semenova, Irina, Ikeda, Kazuho, Resaul, Karim, Kraikivski, Pavel, Aguiar, Mike, Gygi, Steven, Zaliapin, Ilya, Cowan, Ann, Rodionov, Vladimir
Format: Article
Language:English
Subjects:
Animals
Biological Transport
Cell Line
Dyneins - metabolism
Kinesin - metabolism
Melanophores - metabolism
Melanosomes - metabolism
Microtubule-Associated Proteins - metabolism
Microtubules - metabolism
Phosphorylation
Xenopus
Xenopus Proteins - metabolism
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Summary:Microtubule (MT)-based transport of organelles driven by the opposing MT motors kinesins and dynein is tightly regulated in cells, but the underlying molecular mechanisms remain largely unknown. Here we tested the regulation of MT transport by the ubiquitous protein MAP4 using Xenopus melanophores as an experimental system. In these cells, pigment granules (melanosomes) move along MTs to the cell center (aggregation) or to the periphery (dispersion) by means of cytoplasmic dynein and kinesin-2, respectively. We found that aggregation signals induced phosphorylation of threonine residues in the MT-binding domain of the Xenopus MAP4 (XMAP4), thus decreasing binding of this protein to MTs. Overexpression of XMAP4 inhibited pigment aggregation by shortening dynein-dependent MT runs of melanosomes, whereas removal of XMAP4 from MTs reduced the length of kinesin-2-dependent runs and suppressed pigment dispersion. We hypothesize that binding of XMAP4 to MTs negatively regulates dynein-dependent movement of melanosomes and positively regulates kinesin-2-based movement. Phosphorylation during pigment aggregation reduces binding of XMAP4 to MTs, thus increasing dynein-dependent and decreasing kinesin-2-dependent motility of melanosomes, which stimulates their accumulation in the cell center, whereas dephosphorylation of XMAP4 during dispersion has an opposite effect.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.e14-01-0022