Nonredundant roles of DIAPHs in primary ciliogenesis

Oliva Palander,Adam Lam,Richard F Collins,Theo J Moraes,William S Trimble

doi:10.1016/j.jbc.2021.100680

Oliva Palander, Adam Lam + Show 3 more

Open Access

https://doi.org/10.1016/j.jbc.2021.100680

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Abstract

Primary cilia are hubs for several signaling pathways, and disruption in cilia function and formation leads to a range of diseases collectively known as ciliopathies. Both ciliogenesis and cilia maintenance depend on vesicle trafficking along a network of microtubules and actin filaments toward the basal body. The DIAPH (Diaphanous-related) family of formins promote both actin polymerization and microtubule (MT) stability. Recently, we showed that the formin DIAPH1 is involved in ciliogenesis. However, the role of other DIAPH family members in ciliogenesis had not been investigated. Here we show that depletion of either DIAPH2 or DIAPH3 also disrupted ciliogenesis and cilia length. DIAPH3 depletion also reduced trafficking within cilia. To specifically examine the role of DIAPH3 at the base, we used fused full-length DIAPH3 to centrin, which targeted DIAPH3 to the basal body, causing increased trafficking to the ciliary base, an increase in cilia length, and formation of bulbs at the tips of cilia. Additionally, we confirmed that the microtubule-stabilizing properties of DIAPH3 are important for its cilia length functions and trafficking. These results indicate the importance of DIAPH proteins in regulating cilia maintenance. Moreover, defects in ciliogenesis caused by DIAPH depletion could only be rescued by expression of the specific family member depleted, indicating nonredundant roles for these proteins.

Highlights

The initiation of ciliogenesis starts in G1 phase of the cell cycle and cilia continue to grow as cells exit the cell cycle (G0) [12]
We showed that DIAPH1 plays a role in ciliogenesis and cilia maintenance [44], so here we examined whether DIAPH2 and DIAPH3 may play roles in these processes
Since cells were serum starved for 24 h upon depletion of DIAPH2 or DIAPH3, we presumed that the effects of DIAPH2 and DIAPH3 depletion on ciliogenesis and cilia length were not due to cell cycle changes

Summary

Introduction

The initiation of ciliogenesis starts in G1 phase of the cell cycle and cilia continue to grow as cells exit the cell cycle (G0) [12]. We previously observed DIAPH1 localization to the ciliary base, so we examined the localization of DIAPH2 and DIAPH3 in ciliated hTERT-RPE1 cells and compared them to acetylated tubulin and centrin to detect the axoneme and basal body, respectively.

Results

Conclusion