Identification of the Outer-Inner Dynein Linker as a Hub Controller for Axonemal Dynein Activities

Abstract

In flagella, the outer dynein arm (ODA) and inner dynein arm (IDA) play distinct roles in generating beating motion. However, functional communications between the two dyneins have not been investigated. Here, we demonstrated by cryo-electron microscopy and chemical crosslinking that intermediate chain 2 (IC2) of ODAs interacts with the dynein regulatory complex in the axoneme and constitutes part of the outer-inner dynein (OID) linker. Furthermore, we identified IC2 as a functional hub between ODAs and IDAs based on the phenotypes of Chlamydomonas mutants expressing biotinylation-tagged IC2. The flagella of the IC2 mutant showed activated microtubule sliding and enhanced ATPase activities of ODAs, as well as an altered waveform, indicating attenuated IDA activity. We concluded that the OID linker controls both ODAs and IDAs and regulates flagellar beating.