The mouse radial spoke protein 3 is a nucleocytoplasmic shuttling protein that promotes neurogenesis

Abstract

Radial spoke protein 3 (RSP3) was first identified in Chlamydomonas as a component of radial spoke, which is important for flagellar motility. The mammalian homolog of the Chlamydomonas RSP3 protein is found to be a mammalian protein kinase A-anchoring protein that binds ERK1/2. Here we show that mouse RSP3 is a nucleocytoplasmic shuttling protein. The full-length RSP3-EGFP fusion protein is mainly located in the cytoplasm of Chinese hamster ovary cells. However, by using deletion mutants of RSP3, we identified two nuclear localization signals and a nuclear export signal in RSP3. Moreover, using in utero electroporation, we found that overexpression of RSP3 in the developing cerebral cortex promotes neurogenesis. The layer II/III of the neocortex was much thicker in the RSP3-transfected region than that of the untransfected region in the neocortex. We also show that RSP3 is specifically located in the primary cilia of the radial glial cells, where it acts as a signaling mediator that regulates neurogenesis. Thus, our results suggest that RSP3 is a nucleocytoplasmic shuttling protein and plays an essential role in neurogenesis.

Combover interacts with the axonemal component Rsp3 and is required for sperm individualization

“…Loss of polyglycylation on axonemal MTs is accompanied by severe, but variable, progressive loss of MT structures (Rogowski et al, 2009). Although we cannot exclude radial spoke-independent functions of Rsp3 (Yan et al, 2015), it is thus plausible that ICs need the axonemal MTs as tracks to move along the flagella and may become unstable when they are aberrant. At this time, we do not know whether Cmb plays an active role in the actin cones or rather a permissive role on the axonemes for IC progression.…”

CILIA: before and after

“…The classic example is Gli [91] which is localized to the cilium tip, but during hedgehog signaling is specially processed and leaves the cilium to enter the nucleus to affect transcription. Many other signaling molecules including Smad transcription factors [92], p90Rsk [93], Jade 1, a Wnt-related ubiquitin ligase [94], huntingtin [87], parafusin [90], pVHL [95, 96], and RSP3 [97] move from the cilium to the nucleus and sometimes vice versa, meaning that they are recognized and moved past both the ciliary and nuclear barriers. How transport through the cytoplasm between the organelles occurs is unknown—perhaps by diffusion, perhaps requiring cytoskeletal elements and molecular motors.…”

Nuclear roles for cilia-associated proteins

“…As examples, both the ciliary axoneme-associated radial spoke protein 3 (RSPH3–OMIM: 615876) [100] and the pericentriolar and ciliary basal body-associated protein pericentrin (PCNT: OMIM: 605925) [51] have been found to contain functional nuclear localization (NLS) and nuclear exclusion (NES) sequences. Similarly parafusin, a signaling scaffolding protein, has been found localized to the base of primary cilia in a variety of mammalian cell types and within the nuclei of fibroblasts [77].…”