Hu, Jinghua

Background: Autosomal dominant polycystic kidney disease (ADPKD) is a ciliopathy characterized by abnormal tubular epithelial proliferation and fluid secretion. Anoctamin 1 (ANO1) is a calcium-dependent chloride channel. However, how ANO1 contributes to ADPKD is largely unexplored. Methods: Kidney tissues from ADPKD patients, Pkd1RC/RC mice model, WT9-7 human PKD1+⁣/- cells, and 3D culture models in vitro were used. Localization of ANO1 and cilium length were investigated by confocal immunofluorescence. Results: We found that ANO1 was consistently upregulated in human and mouse PKD kidneys. Intriguingly, ANO1 located in a vesicle-like pattern at the ciliary base but not on the ciliary surface. ANO1 deficiency enhanced ciliogenesis and the ciliary dosage of polycystin-2 in human PKD cells, and reduced cyst formation in 3D culture models. Moreover, inhibition of ANO1 abolished the activation of STAT3 and ERK pathways in PKD cells. Conclusions: Our data indicate ANO1 is a negative regulator for both cilia length and cilia trafficking of polycystin-2 and provide mechanistic insights regarding the therapeutic potential of ANO1 pathway in ADPKD treatment.

Skeletal muscle atrophy is commonly associated with aging, immobilization, muscle unloading, and congenital myopathies. Generation of mature muscle cells from skeletal muscle satellite cells (SCs) is pivotal in repairing muscle tissue. Exercise therapy promotes muscle hypertrophy and strength. Primary cilium is implicated as the mechanical sensor in some mammalian cells, but its role in skeletal muscle cells remains vague. To determine mechanical sensors for exercise-induced muscle hypertrophy, we established three SC-specific cilium dysfunctional mouse models— Myogenic factor 5 ( Myf5 ) -Arf-like Protein 3 ( Arl3 ) −/− , Paired box protein Pax-7 ( Pax7 )- Intraflagellar transport protein 88 homolog ( Ift88 ) −/− , and Pax7-Arl3 −/− —by specifically deleting a ciliary protein ARL3 in MYF5-expressing SCs, or IFT88 in PAX7-expressing SCs, or ARL3 in PAX7-expressing SCs, respectively. We show that the Myf5-Arl3 −/− mice develop grossly the same as WT mice. Intriguingly, mechanical stimulation-induced muscle hypertrophy or myoblast differentiation is abrogated in Myf5-Arl3 −/− and Pax7-Arl3 −/− mice or primary isolated Myf5-Arl3 −/− and Pax7-Ift88 −/− myoblasts, likely due to defective cilia-mediated Hedgehog (Hh) signaling. Collectively, we demonstrate SC cilia serve as mechanical sensors and promote exercise-induced muscle hypertrophy via Hh signaling pathway.

Abstract Cellular senescence contributes to tissue homeostasis and age-related pathologies. However, how senescence is initiated in damaged cells remains vague. Here, we discover that irreparable stresses induce transient biogenesis of cilia, which are used by stressed cells to directly communicate with the promyelocytic leukemia nuclear bodies (PML-NBs), the validated stress signaling hub, to initiate senescence responses. Mechanistically, a ciliary ARL13B-ARL3 GTPase cascade negatively regulates the association of transition fiber protein FBF1 and SUMO-conjugating enzyme UBC9. Irreparable stresses downregulate the ciliary ARLs to release UBC9, which SUMOylates FBF1 at the ciliary base. SUMOylated FBF1 then translocates to PML-NBs to promote PML-NB-dependent senescence initiation. Remarkably, Fbf1 suppression effectively subdues global senescence burden and prevents associated health-span decline in irradiation-treated mice. Collectively, our findings assign primary cilia a central role in inducing senescence program and identify them as promising targets to dampen senescence-associated detrimental damage in future senotherapy strategies.

HYLS1 regulates the ciliary phosphoinositide and hedgehog pathways, implicating a novel pathogenic mechanism for HLS syndrome.

The mechanisms underlying E‐cadherin clustering and AJ maturation are not fully understood although the E‐cadherin‐mediated formation of adherens junctions (AJs) is essential for the morphogenesis of epithelial cells. Here we report that the association between type Iγ phosphatidylinositol phosphate kinase (PIPKIγ) and Exo70 regulated the transport and clustering of Ecadherin on the plasma membrane and, subsequently, the extension of nascent E‐cadherin adhesions. We also observed that PI4,5P(2) accumulation at E‐cadherin clusters during the assembly of E‐cadherin adhesions. PIPKIγ‐generated PI4,5P(2) is required for recruiting Exo70 to newly formed E‐cadherin junctions and facilitates the assembly and maturation of AJs. Additionally, Rho activity and actin structure were impaired by loss of Exo70 and/or PIPKIγ. These results support a model in which PIPKIγ and PIPKIγ‐generated PI4,5P(2) pools at nascent E‐cadherin contacts cue Exo70 targeting and orients the tethering of exocyst‐associated E‐cadherin. This could be an important mechanism that regulates E‐cadherin clustering and AJ maturation, and actin reorganization, which is essential for the establishment of solid, polarized epithelial structures.

Although the immune checkpoint role of programmed death ligand 1 (PD-L1) has been established and targeted in cancer immunotherapy, the tumor-intrinsic role of PD-L1 is less appreciated in tumor biology and therapeutics development, partly because of the incomplete mechanistic understanding. Here we demonstrate a potentially novel mechanism by which PD-L1 promotes the epithelial-mesenchymal transition (EMT) in triple-negative breast cancer (TNBC) cells by suppressing the destruction of the EMT transcription factor Snail. PD-L1 directly binds to and inhibits the tyrosine phosphatase PTP1B, thus preserving p38-MAPK activity that phosphorylates and inhibits glycogen synthase kinase 3β (GSK3β). Via this mechanism, PD-L1 prevents the GSK3β-mediated phosphorylation, ubiquitination, and degradation of Snail and consequently promotes the EMT and metastatic potential of TNBC. Significantly, PD-L1 antibodies that confine the tumor-intrinsic PD-L1/Snail pathway restricted TNBC progression in immunodeficient mice. More importantly, targeting both tumor-intrinsic and tumor-extrinsic functions of PD-L1 showed strong synergistic tumor suppression effect in an immunocompetent TNBC mouse model. Our findings support that PD-L1 intrinsically facilitates TNBC progression by promoting the EMT, and this potentially novel PD-L1 signaling pathway could be targeted for better clinical management of PD-L1–overexpressing TNBCs.

AbstractCisplatin nephrotoxicity has been considered as serious side effect caused by cisplatin‐based chemotherapy. Recent evidence indicates that renal tubular cell apoptosis and inflammation contribute to the progression of cisplatin‐induced acute kidney injury (AKI). Hepatocyte nuclear factor 1β (HNF1β) has been reported to regulate the development of kidney cystogenesis, diabetic nephrotoxicity, etc However, the regulatory mechanism of HNF1β in cisplatin nephrotoxicity is largely unknown. In the present study, we examined the effects of HNF1β deficiency on the development of cisplatin‐induced AKI in vitro and in vivo. HNF1β down‐regulation exacerbated cisplatin‐induced RPTC apoptosis by indirectly inducing NF‐κB p65 phosphorylation and nuclear translocation. HNF1β knockdown C57BL/6 mice were constructed by injecting intravenously with HNF1β‐interfering shRNA and PEI. The HNF1β scramble and knockdown mice were treated with 30 mg/kg cisplatin for 3 days to induce acute kidney injury. Cisplatin treatment caused increased caspase 3 cleavage and p65 phosphorylation, elevated serum urea nitrogen and creatinine, and obvious histological damage of kidney such as fractured tubules in control mice, which were enhanced in HNF1β knockdown mice. These results suggest that HNF1β may ameliorate cisplatin nephrotoxicity in vitro and in vivo, probably through regulating NF‐κB signalling pathway.

Background Adolescent idiopathic scoliosis (AIS) is a genetically heterogeneous disease characterised by three-dimensional deformity of the spine in the absence of a congenital spinal anomaly or neurological musculoskeletal disorder. The clinical variability and incomplete penetrance of some genes linked with AIS indicate that this disease constitutes an oligogenic trait. Objective We aimed to explore the oligogenic nature of this disease and identify novel AIS genes. Methods We analysed rare damaging variants within AIS-associated genes by using exome sequencing in 40 AIS trios and 183 sporadic patients. Results Multiple variants within AIS-associated genes were identified in eight AIS trios, and five individuals harboured rare damaging variants in the FLNB gene. The patients showed more frequent oligogenicity than the controls. In the gene-based burden test, the top signal resided in FLNB . In functional studies, we found that the AIS-associated FLNB variants altered the protein’s conformation and subcellular localisation and its interaction with other proteins (TTC26 and OFD1) involved in AIS. The most compelling evidence of an oligogenic basis was that the number of rare damaging variants was recognised as an independent prognostic factor for curve progression in Cox regression analysis. Conclusion Our data indicate that AIS is an oligogenic disease and identify FLNB as a susceptibility gene for AIS.

Primary cilia serve as cellular antenna for various sensory signaling pathways. However, how the sensory receptors are properly targeted to the ciliary surface remains poorly understood. Here, we show that UBC-9, the sole E2 small ubiquitin-like modifier (SUMO)-conjugating enzyme, physically interacts with and SUMOylates the C terminus of small GTPase ARL-13, the worm orthologue of ARL13B that mutated in ciliopathy Joubert syndrome. Mutations that totally abolish the SUMOylation of ARL-13 do not affect its established role in ciliogenesis, but fail to regulate the proper ciliary targeting of various sensory receptors and consequently compromise the corresponding sensory functions. Conversely, constitutively SUMOylated ARL-13 fully rescues all ciliary defects of arl-13–null animals. Furthermore, SUMOylation modification of human ARL13B is required for the ciliary entry of polycystin-2, the protein mutated in autosomal dominant polycystic kidney disease. Our data reveal a novel but conserved role for the SUMOylation modification of ciliary small GTPase ARL13B in specifically regulating the proper ciliary targeting of various sensory receptors.