Organelle-specific control of intracellular transport: distinctly targeted isoforms of the regulator Klar.
Microtubule-based transport in cells is powered by a small set of distinct motors, yet timing and destination of transport can be controlled in a cargo-specific manner. The mechanistic basis for this specificity is not understood. To address this question, we analyzed the Drosophila Klarsicht (Klar) protein that regulates distinct microtubule-based transport processes. We find that localization of Klar to its cargoes is crucial for Klar function. Using mutations, we identify functionally important regions of Klar that confer distinct cargo specificity. In ovaries, Klar is present on the nuclear envelope, a localization that requires the C-terminal KASH domain. In early embryos, Klar is attached to lipid droplets, a localization mediated by a novel C-terminal domain encoded by an alternatively spliced exon. In cultured cells, these two domains are sufficient for targeting to the correct intracellular location. Our analysis disentangles Klar's modular organization: we propose that a core region integral to motor regulation is attached to variable domains so that the cell can target regulators with overlapping, yet distinct functions to specific cargoes. Such isoform variation may be a general strategy for adapting a common regulatory mechanism to specifically control motion and positioning of multiple organelles.
Guo
Yi
Y
Rosenstiel Biomedical Research Center, Brandeis University, Waltham, MA 02454, USA.
Jangi
Sushrut
S
Welte
Michael A
MA
D000483:Alleles; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D019295:Computational Biology; D018076:DNA, Complementary / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins / Q000737:chemistry* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005091:Exons; D005260:Female; D015151:Immunoblotting; D017403:In Situ Hybridization; D050356:Lipid Metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009685:Nuclear Envelope / Q000378:metabolism; D010053:Ovary / Q000378:metabolism; D010641:Phenotype; D011485:Protein Binding; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D000097573:Red Fluorescent Protein
D018076:DNA, Complementary; D029721:Drosophila Proteins; D008164:Luminescent Proteins; D026901:Membrane Transport Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D000097573:Red Fluorescent Protein; C401521:klar protein, Drosophila