Heterogeneity of radial spokes structural components and associated enzymes in Tetrahymena cilia

Radial spokes, RS1-RS2-RS3, are T-shaped, multiprotein complexes that transmit regulatory signals from central apparatus to outer doublet dyneins. RSs, especially RS3, differ in morphology, protein composition, and RS base-docked IDAs. Spokes defects alter cilia beating frequency, waveform, and amplitude leading, in humans, to primary ciliary dyskinesia and infertility. In contrast to RS1 and RS2, the protein composition of RS3 is partly resolved. Moreover, the role of particular spokes is unclear. Ciliate Tetrahymena thermophila has three Rsp3 paralogs and two or three paralogs of some other RSPs. Using multiple complementary approaches, we showed that Tetrahymena forms RS1 and RS2 subtypes having core composed of various Rsp3 paralogs and one type of Rsp3-less RS3. We elucidated proteomes of RS subtypes and identified novel RS-associated proteins, including enzymatic proteins involved in local regulation of the ADP/ATP levels and protein phosphorylation, whose presence further diversifies RSs properties and likely functions.