Heterogeneity of radial spoke components in Tetrahymena cilia.

Radial spokes, RS1, RS2, and RS3, are T-shaped, multiprotein complexes that transmit regulatory signals from the central apparatus to outer doublet complexes, including dynein arms. Radial spokes, especially RS3, differ in their 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 male infertility. The role of the particular spokes remains unclear. Ciliate Tetrahymena thermophila has three RSP3 paralogs and two or three paralogs of some other RSPs. Using multiple complementary approaches, we demonstrated that Tetrahymena forms RS1 and RS2 subtypes, each with a core composed of various RSP3 paralogs and one type of RSP3-less RS3. We elucidated proteomes of RS1 and RS2 subtypes, RS3, and identified novel RS proteins, including enzymatic proteins involved in local regulation of ADP/ATP levels, the guanylate nucleotide pathway, and protein phosphorylation, whose presence further diversifies RSs' properties and likely functions.