1. Dictyostelium LIS1 is a centrosomal protein required for microtubule/cell cortex interactions, nucleus/centrosome linkage, and actin dynamics.
- Author
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Rehberg M, Kleylein-Sohn J, Faix J, Ho TH, Schulz I, and Gräf R
- Subjects
- Amino Acid Sequence, Animals, Cell Shape, Dictyostelium cytology, Gene Expression, Golgi Apparatus metabolism, Green Fluorescent Proteins metabolism, Microscopy, Fluorescence, Microtubule-Associated Proteins chemistry, Microtubule-Associated Proteins genetics, Molecular Sequence Data, Point Mutation, Protein Structure, Tertiary, Protozoan Proteins chemistry, Protozoan Proteins genetics, Sequence Homology, Amino Acid, Actins metabolism, Centrosome metabolism, Dictyostelium chemistry, Microtubule-Associated Proteins physiology, Microtubules metabolism, Protozoan Proteins physiology
- Abstract
The widespread LIS1-proteins were originally identified as the target for sporadic mutations causing lissencephaly in humans. Dictyostelium LIS1 (DdLIS1) is a microtubule-associated protein exhibiting 53% identity to human LIS1. It colocalizes with dynein at isolated, microtubule-free centrosomes, suggesting that both are integral centrosomal components. Replacement of the DdLIS1 gene by the hypomorphic D327H allele or overexpression of an MBP-DdLIS1 fusion disrupted various dynein-associated functions. Microtubules lost contact with the cell cortex and were dragged behind an unusually motile centrosome. Previously, this phenotype was observed in cells overexpressing fragments of dynein or the XMAP215-homologue DdCP224. DdLIS1 was coprecipitated with DdCP224, suggesting that both act together in dynein-mediated cortical attachment of microtubules. Furthermore, DdLIS1-D327H mutants showed Golgi dispersal and reduced centrosome/nucleus association. Defects in DdLIS1 function also altered actin dynamics characterized by traveling waves of actin polymerization correlated with a reduced F-actin content. DdLIS1 could be involved in actin dynamics through Rho-GTPases, because DdLIS1 interacted directly with Rac1A in vitro. Our results show that DdLIS1 is required for maintenance of the microtubule cytoskeleton, Golgi apparatus and nucleus/centrosome association, and they suggest that LIS1-dependent alterations of actin dynamics could also contribute to defects in neuronal migration in lissencephaly patients.
- Published
- 2005
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