Characterization of an IFT particle complex B core protein IFT22 in Chlamydomonas
Xiaomeng Huang1, David Alejandro Silva1, Zhenchuan Fan1, Benjamin D. Engel2, Wallace F. Marshall2, Douglas Cole3, and Hongmin Qin1
1) Department of Biology, Texas A&M University, College Station, TX 77843
2) Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158
3) Dept of Microbiology, Molecular Biology & Biochemistry, University of Idaho, Moscow, ID 83844-3052
Intraflagellar transport (IFT) consists of bidirectionaly movement of large protein particles between the base and the tip of eukaryotic flagella/cilia. Mediating the transport of flagellar precursors and removal of turnover products, IFT is required for the flagella assembly and maintenance. IFT particles are composed of 18 polypeptides which are organized into complex A and B. In this study, we have identified an IFT complex B core protein in Chlamydomonas reinhardtii, IFT22. The knock-down of IFT22 via either miRNA or RNAi results in low growth rates and a high percentage of cells with abnormal size. In addition, in the whole extract, the knock-down cells have greatly reduced levels of almost all the IFT particle proteins and axoneme proteins. In contrast, in the flagella isolated from knock-down cells, the levels of many IFT particle proteins, the anterograde motor protein Fla10 and ubiquitinated proteins are increased. Our data indicate that IFT22 is important for the maintaining the cellular level of both complex A and B, and axonemal proteins, and IFT22 is involved in cell-cycle control and the flagella stability.
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