The established and the predicted roles of dynein light chain in the regulation of mitochondrial apoptosis

DYNLL1 accelerates cell cycle via ILF2/CDK4 axis to promote hepatocellular carcinoma development and palbociclib sensitivity

BACKGROUND

Disorder of cell cycle represents as a major driver of hepatocarcinogenesis and constitutes an attractive therapeutic target. However, identifying key genes that respond to cell cycle-dependent treatments still facing critical challenges in hepatocellular carcinoma (HCC). Increasing evidence indicates that dynein light chain 1 (DYNLL1) is closely related to cell cycle progression and plays a critical role in tumorigenesis. In this study, we explored the role of DYNLL1 in the regulation of cell cycle progression in HCC.

METHODS

We analysed clinical specimens to assess the expression and predictive value of DYNLL1 in HCC. The oncogenic role of DYNLL1 was determined by gain or loss-of-function experiments in vitro, and xenograft tumour, liver orthotopic, and DEN/CCl4-induced mouse models in vivo. Mass spectrometry analysis, RNA sequencing, co-immunoprecipitation assays, and forward and reverse experiments were performed to clarify the mechanism by which DYNLL1 activates the interleukin-2 enhancer-binding factor 2 (ILF2)/CDK4 signalling axis. Finally, the sensitivity of HCC cells to palbociclib and sorafenib was assessed by apoptosis, cell counting kit-8, and colony formation assays in vitro, and xenograft tumour models and liver orthotopic models in vivo.

RESULTS

DYNLL1 was significantly higher in HCC tissues than that in normal liver tissues and closely related to the clinicopathological features and prognosis of patients with HCC. Importantly, DYNLL1 was identified as a novel hepatocarcinogenesis gene from both in vitro and in vivo evidence. Mechanistically, DYNLL1 could interact with ILF2 and facilitate the expression of ILF2, then ILF2 could interact with CDK4 mRNA and delay its degradation, which in turn activates downstream G1/S cell cycle target genes CDK4. Furthermore, palbociclib, a selective CDK4/6 inhibitor, represents as a promising therapeutic strategy for DYNLL1-overexpressed HCC, alone or particularly in combination with sorafenib.

CONCLUSIONS

Our work uncovers a novel function of DYNLL1 in orchestrating cell cycle to promote HCC development and suggests a potential synergy of CDK4/6 inhibitor and sorafenib for the treatment of HCC patients, especially those with increased DYNLL1.

MiR-5622-3p inhibits ZCWPW1 to induce apoptosis in silica-exposed mice and spermatocyte cells

Silica nanoparticles (SiNPs) could cause damage to spermatogenesis, and microRNAs were reported to be associated with male reproduction. This research was designed to explore the toxic impacts of SiNPs induced in male reproduction through miR-5622-3p. In vivo, 60 mice were randomized into the control group and SiNPs group, in which they were exposed to SiNPs for 35 days and then recovered for 15 days. In vitro, 4 groups were set: control group, SiNPs group, SiNPs + miR-5622-3p inhibitor group, and SiNPs + miR-5622-3p inhibitor negative control (NC) group. Our research indicated SiNPs caused the apoptosis of spermatogenic cells, increased level of γ-H2AX, raised the expressions of RAD51, DMC1, 53BP1, and LC8 which were DNA damage repair relative factors, and upregulated Cleaved-Caspase-9 and Cleaved-Caspase-3 levels. Furthermore, SiNPs also elevated the expression of miR-5622-3p but downregulated the level of ZCWPW1. However, miR-5622-3p inhibitor reduced the level of miR-5622-3p, increased the level of ZCWPW1, relieved DNA damage, and depressed the activation of apoptosis pathway, thus, alleviating spermatogenic cells apoptosis caused by SiNPs. The above-mentioned results indicated that SiNPs induced DNA damage resulting in activating of DNA damage response. Meanwhile, SiNPs raised the level of miR-5622-3p targeting inhibited expression of ZCWPW1 to suppress the repair process, possibly making DNA damage so severe that leading to the failure of DNA damage repair, finally inducing the apoptosis of spermatogenic cells.

Label-free quantitative proteomics and immunoblotting identifies immunoreactive and other excretory-secretory (E/S) proteins of Anoplocephala perfoliata

Anoplocephala perfoliata is a common tapeworm in horses causing colic and even mortalities. Current diagnostic tests to detect A. perfoliata infections have their limitations and an improved method is needed. Immunoreactive excretory/secretory proteins (E/S proteome) of this parasite can provide promising candidates for diagnostic tests. We compared E/S proteins produced by small (length < 20 mm, width < 5 mm) and large (length 20 to 40 mm, width 5 to 10 mm) A. perfoliata worms in vitro by label-free quantitative proteomics using a database composed of related Hymenolepis diminuta, Echinococcus multilocularis/granulosus and Taenia aseatica proteins for protein identifications. Altogether, 509 E/S proteins were identified after incubating the worms in vitro for three and eight hours. The greatest E/S proteome changes suggested both worm size- and time-dependent changes in cytoskeleton remodeling, apoptosis, and production of antigens/immunogens. The E/S proteins collected at the three-hour time point represented the natural conditions better than those collected at the eight-hour time point, and thereby contained the most relevant diagnostic targets. Immunoblotting using antibodies from horses tested positive/negative for A. perfoliata indicated strongest antigenicity/immunogenicity with 13-, 30- and 100-kDa proteins, involving a thioredoxin, heat-shock chaperone 90 (Hsp90), dynein light chain component (DYNLL), tubulin-specific chaperone A (TBCA) and signaling pathway modulators (14-3-3 and Sj-Ts4). This is among the first studies identifying new diagnostic targets and A. perfoliata antigens eliciting a IgG-response in horses.

The interaction between LC8 and LCA5 reveals a novel oligomerization function of LC8 in the ciliary-centrosome system

Dynein light chain LC8 is a small dimeric hub protein that recognizes its partners through short linear motifs and is commonly assumed to drive their dimerization. It has more than 100 known binding partners involved in a wide range of cellular processes. Recent large-scale interaction studies suggested that LC8 could also play a role in the ciliary/centrosome system. However, the cellular function of LC8 in this system remains elusive. In this work, we characterized the interaction of LC8 with the centrosomal protein lebercilin (LCA5), which is associated with a specific form of ciliopathy. We showed that LCA5 binds LC8 through two linear motifs. In contrast to the commonly accepted model, LCA5 forms dimers through extensive coiled coil formation in a LC8-independent manner. However, LC8 enhances the oligomerization ability of LCA5 that requires a finely balanced interplay of coiled coil segments and both binding motifs. Based on our results, we propose that LC8 acts as an oligomerization engine that is responsible for the higher order oligomer formation of LCA5. As LCA5 shares several common features with other centrosomal proteins, the presented LC8 driven oligomerization could be widespread among centrosomal proteins, highlighting an important novel cellular function of LC8.

Extended N-Terminal Acetyltransferase Naa50 in Filamentous Fungi Adds to Naa50 Diversity

Most eukaryotic proteins are N-terminally acetylated by a set of Nα acetyltransferases (NATs). This ancient and ubiquitous modification plays a fundamental role in protein homeostasis, while mutations are linked to human diseases and phenotypic defects. In particular, Naa50 features species-specific differences, as it is inactive in yeast but active in higher eukaryotes. Together with NatA, it engages in NatE complex formation for cotranslational acetylation. Here, we report Naa50 homologs from the filamentous fungi Chaetomium thermophilum and Neurospora crassa with significant N- and C-terminal extensions to the conserved GNAT domain. Structural and biochemical analyses show that CtNaa50 shares the GNAT structure and substrate specificity with other homologs. However, in contrast to previously analyzed Naa50 proteins, it does not form NatE. The elongated N-terminus increases Naa50 thermostability and binds to dynein light chain protein 1, while our data suggest that conserved positive patches in the C-terminus allow for ribosome binding independent of NatA. Our study provides new insights into the many facets of Naa50 and highlights the diversification of NATs during evolution.

DLEU1 promotes cell survival by preventing DYNLL1 degradation in esophageal squamous cell carcinoma

BACKGROUND

Emerging evidence has highlighted the critical roles of long noncoding RNAs (lncRNAs) in tumor development and progression. However, the biological functions and underlying mechanisms of DLEU1 in esophageal squamous cell carcinoma (ESCC) remain unclear.

METHODS

LncRNA expression in ESCC tissues was explored using lncRNA microarray datasets. The functional roles of DLEU1 in ESCC were demonstrated by a series of in vitro and in vivo experiments. RNA pull-down and immunoprecipitation assays were performed to demonstrate the potential mechanisms of DLEU1.

RESULTS

In a screen for differentially expressed lncRNAs in ESCC, we determined that DLEU1 was one of the most overexpressed lncRNAs in ESCC tissues and that upregulated DLEU1 expression was associated with a worse prognosis. Functional assays showed that DLEU1 promoted tumor growth by inhibiting cell apoptosis. Mechanistically, DLEU1 could bind and stabilize DYNLL1 by interfering with RNF114-mediated ubiquitination and proteasomal degradation. The DLEU1/DYNLL1 axis subsequently upregulated antiapoptotic BCL2 and promoted cell survival. Furthermore, DLEU1 upregulation was at least partly facilitated by promoter hypomethylation. Notably, targeting DLEU1 sensitized ESCC cells to cisplatin-induced death.

CONCLUSIONS

Our findings suggest that DLEU1-mediated stabilization of DYNLL1 is critical for cell survival and that the DLEU1/DYNLL1 axis may be a promising therapeutic target for ESCC.

Molecular Cloning of Dynein Heavy Chain and the Effect of Dynein Inhibition on the Testicular Function of Portunus trituberculatus

Simple Summary

Portunus trituberculatus is a very important marine economic species. The study of its reproductive biology can provide a theoretical basis for its breeding. Dynein is a member of the motor protein family. It plays an important role in various life activities, such as cell division and intracellular material transport. In order to study the role of dynein in the testis of Portunus trituberculatus, we cloned the heavy chain of dynein and used the dynein inhibitor sodium orthovanadate to make the dynein lose its function. By detecting the localization of dynein, as well as the detection of various apoptosis indexes, antioxidant stress indexes and immune indexes, this study proved that dynein is essential in testis.

Abstract

Dynein is a motor protein with multiple transport functions. However, dynein’s role in crustacean testis is still unknown. We cloned the full-length cDNA of cytoplasmic dynein heavy chain (Pt-dhc) gene and its structure was analyzed. Its expression level was highest in testis. We injected the dynein inhibitor sodium orthovanadate (SOV) into the crab. The distribution of Portunus trituberculatus dynein heavy chain (Pt-DHC) in mature sperm was detected by immunofluorescence. The apoptosis of spermatids was detected using a TUNEL kit; gene expression in testis was detected by fluorescence quantitative PCR (qPCR). The expression of immune-related factors in the testis were detected by an enzyme activity kit. The results showed that the distribution of Pt-DHC was abnormal after SOV injection, indicating that the function of dynein was successfully inhibited. Apoptosis-related genes p53 and caspase-3, and antioxidant stress genes HSP70 and NOS were significantly decreased, and anti-apoptosis gene bcl-2 was significantly increased. The activities of superoxide dismutase (SOD) and alkaline phosphatase (AKP) were significantly decreased. The results showed that there was no apoptosis in testicular cells after dynein function was inhibited, but the cell function was disordered. This study laid a theoretical foundation for the further study of apoptosis in testis and the function of dynein in testis and breeding of P. trituberculatus.

Linalool-Loaded Glutathione-Modified Gold Nanoparticles Conjugated with CALNN Peptide as Apoptosis Inducer and NF-κB Translocation Inhibitor in SKOV-3 Cell Line

Background

Linalool is a monoterpene compound with various potential therapeutic applications in several medical fields. Previous studies have indicated the activity of linalool against cell lines; however, its high level of toxicity restricts its use. The aim of this study was to design and manufacture compounds with a novel structure that can be used for loading linalool, to reduce its toxicity and improve its reachable ability.

Methods

We synthesized and characterized a new molecule for loading linalool onto gold nanoparticles (GNPs) capped with glutathione and conjugated with a CALNN peptide. Linalool was loaded onto the GNPs via the reaction of the surface groups of both linalool and the GNPs. Moreover, the target peptide could be loaded onto the surface of the GNPs via a chemical reaction. The cytotoxic effects of linalool–GNP (LG) and linalool–GNP–CALNN peptide (LGC) conjugates against ovarian cancer cells were investigated, as were the possible mechanisms underlying the induction of apoptosis.

Results

Our findings illustrated the significant antiproliferative effect of LG and LGC on SKOV-3 cells. The cytotoxicity assay demonstrated that LG and LGC were selectively toxic in cancer cells and induced apoptosis by activating caspase-8, the p53 protein, and various proteins involved in apoptosis. The present data demonstrated that LG and LGC have a high therapeutic potential and should be given particular consideration as anticancer drug-delivery systems, as LG and LGC were remarkably more cytotoxic against a cancer cell line than were linalool and GNPs alone.

Conclusion

We concluded that LG and LGC are promising compounds that can be used for treating ovarian cancer (SKOV-3) cells via the induction of apoptosis through extrinsic and intrinsic pathways.

DYNLL1 is hypomethylated and upregulated in a tumor stage- and grade-dependent manner and associated with increased mortality in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and cellular mechanisms regulating HCC pathogenesis and progression are not completely understood. DYNLL1 is essential for the development and expansion of MYC-driven B cell lymphoma, and also regulates genomic stability and responses to DNA-damaging chemotherapy in BRCA1-deficient tumors. However, the role and regulation of DYNLL1 has not been previously studied in the context of HCC. Here we report that DYNLL1 gene is hypomethylated and its expression is upregulated in HCC patients compared to healthy controls. The expression of DYNLL1 changes in a tumor grade- and stage-dependent manner in HCC. In this study, we further show that high DYNLL1 expression results in shorter overall and progression-free survival in hepatocellular carcinoma patients. Similar to DYNLL1, one of its protein interactors, RACK1, also shows decreased CpG-aggregated methylation and increased expression in HCC. RACK1 expression increases from early to late stage and from low to high grade in HCC. We found that high RACK1 expression is significantly associated with increased mortality of HCC patients. The present study shows that the epigenetic regulation of DYNLL1 and its consequent upregulation might be contributing to cancer development and progression in HCC. Its higher expression in late stage or high grade HCC may favor more aggressive disease as pointed by the increased mortality in high expression cohort. A better mechanistic understanding of the role of DYNLL1 in HCC will be needed to develop targeted treatment strategies in the future.

Dynein light chain binding determines complex formation and posttranslational stability of the Bcl-2 family members Bmf and Bim

The BH3-only class of Bcl-2 family proteins triggers mitochondrial apoptosis. Several mechanisms are used to restrain the pro-apoptotic activity of these proteins. Dynein light chain (DYNLL) 1 and 2 has been proposed to negatively regulate the activity of Bim and Bmf, respectively, and the Bim-DYNLL1 interaction leads to the formation of large protein complexes on mitochondria. Here we found that Bim and Bmf interact with both isoforms of DYNLL (DYNLL1 and DYNLL2). DYNLL1/2 not only induced homo-dimerization of Bim and Bmf but also led to the formation of ternary complexes (Bim-DYNLL-Bmf), both in cell-free and in cellular systems. DYNLL-induced oligomerization stabilized Bmf in cultured cells and inhibited its degradation by the ubiquitin-independent 20S proteasome in a cell-free system. Surprisingly, overexpression of wild-type Bmf but not of a DYNLL-binding-deficient mutant induced degradation of endogenous Bim in different cell lines, but both variants sensitized to apoptosis. Mutant Bmf incapable of interacting with anti-apoptotic Bcl-2 proteins and of inducing apoptosis still caused Bim degradation. These results suggest that Bmf overexpression-induced Bim degradation is not due to the displacement of Bim from anti-apoptotic Bcl-2 proteins but a direct consequence of the modulation of Bim-DYNLL association. A peptide derived from the DYNLL-binding domain of Bim also led to the degradation of Bim as well as of its preferred binding partner Mcl-1. Thus DYNLL regulates the mitochondrial pathway of apoptosis by determining the stability of Bmf, Bim, and Mcl-1 proteins.