Functional partitioning of a liquid-like organelle during assembly of axonemal dyneins

Abstract

Ciliary motility is driven by axonemal dyneins that are assembled in the cytoplasm before deployment to cilia. Motile ciliopathy can result from defects in the dyneins themselves or from defects in factors required for their cytoplasmic pre-assembly. Recent work demonstrates that axonemal dyneins, their specific assembly factors, and broadly acting chaperones are concentrated in liquid-like organelles in the cytoplasm called DynAPs. Here, we use in vivo imaging to show that inner dynein arm (IDA) and outer dynein arm (ODA) subunits are partitioned into non-overlapping sub-regions within DynAPs. Using affinity purification massspectrometry of in vivo interaction partners, we also identify novel partners for inner and outer dynein arms. Among these, we identify C16orf71/Daap1 as a novel axonemal dynein regulator. Daap1 interacts with ODA subunits, localizes specifically to the cytoplasm, is enriched in DynAPs, and is required for the deployment of ODAs to axonemes. Our work reveals a new complexity in the structure and function of a cell-type specific liquid-like organelle that is directly relevant to a human genetic disease.

Shulin packages axonemal outer dynein arms for ciliary targeting

“…Q22MS1 is a 222 kDa protein containing a catalytically inactive nucleoside diphosphate kinase (NDK) domain. A homologous NDK domain is found in the recently identified Xenopus protein DAAP1 (21). DAAP1 has also been implicated in ODA delivery to cilia and localizes to membrane-less organelles involved in dynein assembly.…”

Analysis of small EV proteomes reveals unique functional protein networks regulated by VAP-A

“…While these func�onal complexes retain the vast majority of SF3A3 in the nucleus for splicing, a small amount of SF3A3 can be detected in the cytoplasmic frac�on of cellular lysates [23] where it might be trafficked to sites of EV biogenesis. In fact, in the mul�ciliated cells of Xenopus epithelium, SF3A3 localizes to specialized cytoplasmic granules called dynein axonemal par�cles [24]. SF3A3 has also been shown to redistribute to the cytoplasm upon ubiqui�na�on [23] and through interac�on with the tumor suppressor protein CSR1 [25].…”

Shulin packages axonemal outer dynein arms for ciliary targeting

“…It is 222 kDa in size and contains a catalytically inactive nucleoside diphosphate kinase (NDK) domain. A homologous NDK domain is found in the recently identified Xenopus protein DAAP1 (23). DAAP1 has also been implicated in ODA delivery to cilia and localizes to membraneless organelles involved in dynein assembly.…”