Redistribution of the kinesin-II subunit KAP from cilia to nuclei during the mitotic and ciliogenic cycles in sea urchin embryos.
KAP is the non-motor subunit of the heteromeric plus-end directed microtubule (MT) motor protein kinesin-II essential for normal cilia formation. Studies in Chlamydomonas have demonstrated that kinesin-II drives the anterograde intraflagellar transport (IFT) of protein complexes along ciliary axonemes. We used a green fluorescent protein (GFP) chimera of KAP, KAP-GFP, to monitor movements of this kinesin-II subunit in cells of sea urchin blastulae where cilia are retracted and rebuilt with each mitosis. As expected if involved in IFT, KAP-GFP localized to apical cytoplasm, basal bodies, and cilia and became concentrated on basal bodies of newly forming cilia. Surprisingly, after ciliary retraction early in mitosis, KAP-GFP moved into nuclei before nuclear envelope breakdown, was again present in nuclei after nuclear envelope reformation, and only decreased in nuclei as ciliogenesis reinitiated. Nuclear transport of KAP-GFP could be due to a putative nuclear localization signal and nuclear export signals identified in the sea urchin KAP primary sequence. Our observation of a protein involved in IFT being imported into the nucleus after ciliary retraction and again after nuclear envelope reformation suggests KAP115 may serve as a signal to the nucleus to reinitiate cilia formation during sea urchin development.
Morris
Robert L
RL
Department of Biology, Wheaton College, Norton, MA 02766, USA. rmorris@wheatonma.edu
English
Christopher N
CN
Lou
Julia E
JE
Dufort
Fay J
FJ
Nordberg
Joshua
J
Terasaki
Mark
M
Hinkle
Beth
B
D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism*; D030541:Databases, Genetic; D003911:Dextrans / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism / Q000502:physiology; D049452:Green Fluorescent Proteins; D007091:Image Processing, Computer-Assisted; D016547:Kinesins; D008164:Luminescent Proteins; D008845:Microinjections; D018613:Microscopy, Confocal; D008938:Mitosis / Q000502:physiology*; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D012235:Rhodamines / Q000378:metabolism; D012617:Sea Urchins / Q000196:embryology*; D016415:Sequence Alignment; D013997:Time Factors
D002135:Calcium-Binding Proteins; D003911:Dextrans; D008164:Luminescent Proteins; D009124:Muscle Proteins; D012235:Rhodamines; C074152:kinesin-II; D049452:Green Fluorescent Proteins; D016547:Kinesins