Cilia dysfunction leads to chronic lung disease, as occurs in the genetic syndrome primary ciliary dyskinesis (PCD) and may contribute to impaired airway clearance in obstructive pulmonary disease (COPD). Unlike cystic fibrosis, which also causes chronic airway destruction, there is no specific therapy for cilia-related diseases. We now know that most PCD mutations result in defective production, transport, or proper placement of ciliary motors along the ciliary axoneme. However, the exact mechanism by which this occurs is not understood, impeding the development of cilia-specific therapeutic strategies. Thus, our goal is to determine how ciliary motor components are directed from the cytoplasm, into the cilia, then find their way to specific sites along the ciliary axoneme. In this proposal, we trace the passage of the multifunctional, heterodimer CCDC39/CCDC40, which when mutant result in disorganized axonemal microtubule structure and severe PCD disease. CCDC39 trafficking serves to identify the mechanisms by which ciliary components move from the cytoplasm, en route to the basal body, and into cilia by intraflagellar transport (IFT). Our preliminary data indicate that: (1) Ciliary cargoes, including CCDC39, bind centriolar satellite proteins that function as ?cars? to facilitate trafficking to the basal body; (2) CCDC39/CCDC40 are linked to microtubules in association with two novel ?staple? proteins; and (3) CCDC39 is an IFT co-adaptor protein, with ciliary protein MLF1, for cargo delivery to cilia. We hypothesize that movement of ciliary cargo from the cytoplasm to cilia engages transport mechanisms using satellite proteins, then co-adapter proteins, including CCDC39/CCDC40, to properly assemble cilia. We will characterize this series of pathways in the Specific Aims: (1) Determine how components of motile cilia are trafficked from the cytoplasm to basal bodies; (2) Characterize the multifunctional protein CCDC39 by biophysical and biochemical means that will identify the role of novel staple proteins; and (3) Identify the role for CCDC39 and MLF1 as IFT co-adapter proteins in PCD mutants and COPD tissues. The project uses highly integrated strategies that employ models from single cell organisms to human tissues carried out by the multidisciplinary Washington University Cilia Group, to define new pathways for cilia assembly that can be translated to therapies.
Clearance of pathogens and particulates from the airway is an essential function for host defense, and dependent on the combined actions of airway mucus and beating cilia. Genetic defects in cilia function result in lung infection and the development of chronic lung disease. We identify key mechanisms for the assembly of motile cilia that provide critical points of control, identify causes for genetic motile cilia disease that can be adapted as targets for therapy of defective cilia.
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