CCTalpha and CCTdelta chaperonin subunits are essential and required for cilia assembly and maintenance in Tetrahymena.
BACKGROUND
The eukaryotic cytosolic chaperonin CCT is a hetero-oligomeric complex formed by two rings connected back-to-back, each composed of eight distinct subunits (CCTalpha to CCTzeta). CCT complex mediates the folding, of a wide range of newly synthesised proteins including tubulin (alpha, beta and gamma) and actin, as quantitatively major substrates.


RESULTS
We disrupted the genes encoding CCTalpha and CCTdelta subunits in the ciliate Tetrahymena. Cells lacking the zygotic expression of either CCTalpha or CCTdelta showed a loss of cell body microtubules, failed to assemble new cilia and died within 2 cell cycles. We also show that loss of CCT subunit activity leads to axoneme shortening and splaying of tips of axonemal microtubules. An epitope-tagged CCTalpha rescued the gene knockout phenotype and localized primarily to the tips of cilia. A mutation in CCTalpha, G346E, at a residue also present in the related protein implicated in the Bardet Biedel Syndrome, BBS6, also caused defects in cilia and impaired CCTalpha localization in cilia.


CONCLUSIONS
Our results demonstrate that the CCT subunits are essential and required for ciliary assembly and maintenance of axoneme structure, especially at the tips of cilia.
Seixas
Cecilia
C
Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Cruto
Teresa
T
Tavares
Alexandra
A
Gaertig
Jacek
J
Soares
Helena
H
D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D054468:Axoneme / Q000378:metabolism / Q000473:pathology; D056404:Chaperonin Containing TCP-1 / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism*; D000939:Epitopes / Q000378:metabolism; D055786:Gene Knockout Techniques; D008870:Microtubules / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D021122:Protein Subunits / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013696:Temperature; D013768:Tetrahymena / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D015053:Zygote / Q000166:cytology / Q000378:metabolism
D000939:Epitopes; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D056404:Chaperonin Containing TCP-1