CP ASSEMBLY IN CILIA · Role of the tubulin posttranslational modifications and microtubule severing protein, katanin in the cilia central pair assembly

Cilia are microtubule (MT)-based external cell extensions that perform sensory and locomotory functions. Disruption of ciliary beating leads to human disorders such as infertility, airways diseases and hydrocephalus. The central pair of MTs (CP) apparatus is required for proper cilia motility yet the molecular mechanism that regulates its assembly is unknown. Loss of function mutations of MTs severing protein katanin or changes in the levels of MTs posttranslational modifications (PTMs) result in assembly of short immotile cilia that lack CP. Tubulin PTMs affect activity of katanin toward cytoplasmic MTs but the role of katanin and tubulin PTMs in ciliogenesis is unknown. Thus our main goal is to determine the role of katanin and tubulin PTMs and their reciprocal relationships during ciliogenesis, and their effect on the assembly and/or stability of CP MTs. We intend to identify katanin ciliary localization domain and ciliary interacting proteins. We will use a well established model to analyze motile cilia, a ciliate Tetrahymena thermophila. We will take advantage of high resolution microscopy for localization studies. We will perform mutagenesis analysis of katanin and b-tubulin in order to identified the key amino acid(s) involved in ciliary localization and interactions between these two proteins in cilia. To determine if defects in cilia caused by b-tubulin or katanin mutations can be rescued by parallel mutations in katanin and b-tubulin, respectively and restore disrupted protein interactions we will mutate katanin (or b-tubulin) and express under inducible promoter in wild-type and loss of function mutation background of partner protein. The outcome of the project will have likely medical implications. The project links different aspects of my postdoctoral research and will enhance the research potential of the Host Organization, provide foundation for competitive research program and will become a stepping stone into building an independent research group.