CYLD mediates ciliogenesis in multiple organs by deubiquitinating Cep70 and inactivating HDAC6

Abstract

Cilia are hair-like organelles extending from the cell surface with important sensory and motility functions. Ciliary defects can result in a wide range of human diseases known as ciliopathies. However, the molecular mechanisms controlling ciliogenesis remain poorly defined. Here we show that cylindromatosis (CYLD), a tumor suppressor protein harboring deubiquitinase activity, plays a critical role in the assembly of both primary and motile cilia in multiple organs. CYLD knockout mice exhibit polydactyly and various ciliary defects, such as failure in basal body anchorage and disorganization of basal bodies and axenomes. The ciliary function of CYLD is partially attributed to its deconjugation of the polyubiquitin chain from centrosomal protein of 70 kDa (Cep70), a requirement for Cep70 to interact with γ-tubulin and localize at the centrosome. In addition, CYLD-mediated inhibition of histone deacetylase 6 (HDAC6), which promotes tubulin acetylation, constitutes another mechanism for the ciliary function of CYLD. Small-molecule inhibitors of HDAC6 could partially rescue the ciliary defects in CYLD knockout mice. These findings highlight the importance of protein ubiquitination in the modulation of ciliogenesis, identify CYLD as a crucial regulator of this process, and suggest the involvement of CYLD deficiency in ciliopathies.

CYLD – a deubiquitylase that acts to fine-tune microtubule properties and functions

“…Moreover, Cyld-knockout mice have strikingly different phenotypes than transgenic mice that carry truncations in the C-terminal deubiquitylase domain. For example, Cyld-knockout mice are viable, whereas C-terminal truncations of CYLD lead to embryonic lethality (Eguether et al, 2014;Jin et al, 2008;Lim et al, 2007;Massoumi et al, 2006;Reiley et al, 2006;Trompouki et al, 2009;Wright et al, 2007;Yang et al, 2014b;Zhang et al, 2006). In agreement with these findings, several studies have shown that the N-terminal CAP-Gly domains of CYLD mediate its interaction with microtubules and that these domains are required for its physiological and pathological functions.…”

“…Recently, two independent studies using different mouse models have shown that CYLD is required for ciliogenesis. We have found that Cyld-knockout mice exhibit polydactyly, a cilium-associated symptom (Malik, 2014), and defective ciliogenesis in multiple organs, including the skin, kidney, trachea and testis (Yang et al, 2014b). Transmission electron microscopy showed that CYLD is required for the anchorage of the basal body and proper organization of the basal body and axoneme (Fig.…”

Mechanisms of regulation and diversification of deubiquitylating enzyme function

“…At the same time, CYLD can also interact with several centrosomal proteins, such as CEP192 (Gomez-Ferreria et al, 2012), CAP350 (also known as CEP350) (Eguether et al, 2014) and CEP70 (Yang et al, 2014b), and this centrosomal pool of CYLD has been shown to regulate primary cilia formation and mitotic spindle assembly and/or orientation (Eguether et al, 2014;Gomez-Ferreria et al, 2012;Yang et al, 2014a,b). Similarly, USP15 deubiquitylates histone H2B in the nucleus (Long et al, 2014), prevents degradation of the transcriptional repressor RE1-silencing-transcription-factor (REST) at the ribosome (Faronato et al, 2013), as well as opposes RNF26-mediated ubiquitylation of p62 (also known as SQSTM1) at the ER, thus regulating the mobility of endosomes (Jongsma et al, 2016).…”

NudC regulates actin dynamics and ciliogenesis by stabilizing cofilin 1

“…Immunoprecipitation was performed as previously described [46,47]. In brief, cells transfected with the indicated vectors were subjected to immunoprecipitation with anti-Flag antibody-coupled beads (Sigma).…”