Catherine A. Perrone

The N-DRC forms a conserved biochemical complex that maintains outer doublet alignment and limits microtubule sliding in motile axonemes

The nexin–dynein regulatory complex (N-DRC) is implicated in the control of dynein activity as a structural component of the nexin link. This study identifies several new subunits of the N-DRC and demonstrates for the first time that it forms a discrete biochemical complex that maintains outer doublet integrity and regulates microtubule sliding.

IC138 Defines a Subdomain at the Base of the I1 Dynein That Regulates Microtubule Sliding and Flagellar Motility

To understand the mechanisms that regulate the assembly and activity of flagellar dyneins, we focused on the I1 inner arm dynein (dynein f) and a null allele, bop5-2, defective in the gene encoding the IC138 phosphoprotein subunit. I1 dynein assembles in bop5-2 axonemes but lacks at least four subunits: IC138, IC97, LC7b, and flagellar-associated protein (FAP) 120--defining a new I1 subcomplex. Electron microscopy and image averaging revealed a defect at the base of the I1 dynein, in between radial spoke 1 and the outer dynein arms. Microtubule sliding velocities also are reduced. Transformation with wild-type IC138 restores assembly of the IC138 subcomplex and rescues microtubule sliding. These observations suggest that the IC138 subcomplex is required to coordinate I1 motor activity. To further test this hypothesis, we analyzed microtubule sliding in radial spoke and double mutant strains. The results reveal an essential role for the IC138 subcomplex in the regulation of I1 activity by the radial spoke/phosphorylation pathway.

The role of the dynein light intermediate chain in retrograde IFT and flagellar function in Chlamydomonas

D1bLIC is a subunit of the retrograde IFT motor. Knockdown or knockout of D1bLIC has dose-dependent effects on flagellar assembly, length, motility, and signaling. iTRAQ-based proteomics identifies novel proteins altered in d1blic mutant flagella. TIRF microscopy reveals the kinetics and remodeling of the retrograde motor at the flagellar tip.