Prohibitin 1 regulates tumor cell apoptosis via the interaction with X-linked inhibitor of apoptosis protein

Employing non-targeted interactomics approach and subcellular fractionation to increase our understanding of the ghost proteome

Eukaryotic mRNA has long been considered monocistronic, but nowadays, alternative proteins (AltProts) challenge this tenet. The alternative or ghost proteome has largely been neglected and the involvement of AltProts in biological processes. Here, we used subcellular fractionation to increase the information about AltProts and facilitate the detection of protein-protein interactions by the identification of crosslinked peptides. In total, 112 unique AltProts were identified, and we were able to identify 220 crosslinks without peptide enrichment. Among these, 16 crosslinks between AltProts and Referenced Proteins (RefProts) were identified. We further focused on specific examples such as the interaction between IP_2292176 (AltFAM227B) and HLA-B, in which this protein could be a potential new immunopeptide, and the interactions between HIST1H4F and several AltProts which can play a role in mRNA transcription. Thanks to the study of the interactome and the localization of AltProts, we can reveal more of the importance of the ghost proteome.

Inner mitochondrial membrane protein Prohibitin 1 mediates Nix-induced, Parkin-independent mitophagy

Autophagy of damaged mitochondria, called mitophagy, is an important organelle quality control process involved in the pathogenesis of inflammation, cancer, aging, and age-associated diseases. Many of these disorders are associated with altered expression of the inner mitochondrial membrane (IMM) protein Prohibitin 1. The mechanisms whereby dysfunction occurring internally at the IMM and matrix activate events at the outer mitochondrial membrane (OMM) to induce mitophagy are not fully elucidated. Using the gastrointestinal epithelium as a model system highly susceptible to autophagy inhibition, we reveal a specific role of Prohibitin-induced mitophagy in maintaining intestinal homeostasis. We demonstrate that Prohibitin 1 induces mitophagy in response to increased mitochondrial reactive oxygen species (ROS) through binding to mitophagy receptor Nix/Bnip3L and independently of Parkin. Prohibitin 1 is required for ROS-induced Nix localization to mitochondria and maintaining homeostasis of epithelial cells highly susceptible to mitochondrial dysfunction.

The Role of TRIP6, ABCC3 and CPS1 Expression in Resistance of Ovarian Cancer to Taxanes

The main problem precluding successful therapy with conventional taxanes is de novo or acquired resistance to taxanes. Therefore, novel experimental taxane derivatives (Stony Brook taxanes; SB-Ts) are synthesized and tested as potential drugs against resistant solid tumors. Recently, we reported alterations in ABCC3, CPS1, and TRIP6 gene expression in a breast cancer cell line resistant to paclitaxel. The present study aimed to investigate gene expression changes of these three candidate molecules in the highly resistant ovarian carcinoma cells in vitro and corresponding in vivo models treated with paclitaxel and new experimental Stony Brook taxanes of the third generation (SB-T-121605 and SB-T-121606). We also addressed their prognostic meaning in ovarian carcinoma patients treated with taxanes. We estimated and observed changes in mRNA and protein profiles of ABCC3, CPS1, and TRIP6 in resistant and sensitive ovarian cancer cells and after the treatment of resistant ovarian cancer models with paclitaxel and Stony Brook taxanes in vitro and in vivo. Combining Stony Brook taxanes with paclitaxel caused downregulation of CPS1 in the paclitaxel-resistant mouse xenograft tumor model in vivo. Moreover, CPS1 overexpression seems to play a role of a prognostic biomarker of epithelial ovarian carcinoma patients’ poor survival. ABCC3 was overexpressed in EOC tumors, but after the treatment with taxanes, its up-regulation disappeared. Based on our results, we can suggest ABCC3 and CPS1 for further investigations as potential therapeutic targets in human cancers.

Spatial Stable Isotopic Labeling by Amino Acids in Cell Culture: Pulse-Chase Labeling of Three-Dimensional Multicellular Spheroids for Global Proteome Analysis

Three-dimensional cell cultures, or spheroids, are important model systems for cancer research because they recapitulate chemical and phenotypic aspects of in vivo tumors. Spheroids develop radially symmetric chemical gradients, resulting in distinct cellular populations. Stable isotopic labeling by amino acids in cell culture (SILAC) is a well-established approach to quantify protein expression and has previously been used in a pulse-chase format to evaluate temporal changes. In this article, we demonstrate that distinct isotopic signatures can be introduced into discrete spatial cellular populations, effectively tracking proteins to original locations in the spheroid, using a platform that we refer to as spatial SILAC. Spheroid populations were grown with light, medium, and heavy isotopic media, and the concentric shells of cells were harvested by serial trypsinization. Proteins were quantitatively analyzed by ultraperformance liquid chromatography-tandem mass spectrometry. The isotopic signatures correlated with the spatial location and the isotope position do not significantly impact the proteome of each individual layer. Spatial SILAC can be used to examine the proteomic changes in the different layers of the spheroid and to identify protein biomarkers throughout the structure. We show that SILAC labels can be discretely pulsed to discrete positions, without altering the spheroid's proteome, promising future combined pharmacodynamic and pharmacokinetic studies.

The Ethyl Acetate Extract From Celastrus orbiculatus Promotes Apoptosis of Gastric Cancer Cells Through Mitochondria Regulation by PHB

Objective: To investigate the effect of ethyl acetate extract from Celastrus orbiculatus (COE) on gastric cancer cell apoptosis and reveal its underlying molecular mechanism. In addition, it was aimed to stablish a theoretical basis for the clinical application of Celastrus orbiculatus in the gastric cancer treatment. Material and Methods: Western blot and RT-qPCR were used to detect mRNA and protein expression of PHB in gastric cancer and adjacent tissues. MTT method was used to detect the COE effect on the proliferation of AGS cells and to determine the 50% inhibitory concentration COE on these cells. COE effect on AGS apoptosis was evaluated by flow cytometry. Changes in apoptosis-related proteins expression in AGS cells were detected by western blot and changes in mitochondrial membrane potential were detected by JC-1 fluorescence staining. PHB expression was knocked down in AGS cells by lentiviral-mediated RNA interference. The COE antitumor effect was assessed in vivo using a subcutaneous transplantation tumor model in nude mice and in vivo fluorescence tracing technique in small animals. Results: The clinical samples analysis results showed that the PHB expression in gastric cancer samples was significantly higher than in corresponding adjacent tissues. MTT results showed that the AGS cell proliferation was significantly inhibited. RT-qPCR and western blot results showed that COE can significantly inhibit the PHB mRNA and protein expression, respectively. Flow cytometry analysis showed that COE was able to significantly promote AGS cell apoptosis. Western blot results also indicated that apoptosis-related protein expression changed significantly; BCL-2 expression significantly reduced while the Caspase-3 and Bax expression significantly increased after COE treatment. JC-1 fluorescence staining results showed that COE changed the mitochondrial membrane potential and activated the mitochondrial apoptosis pathway. Furthermore, in vivo experiments results demonstrated that the growth of subcutaneous transplanted tumor was significantly inhibited by the PHB knockdown and by the COE intragastric administration. Conclusion: COE can significantly promote apoptosis of human gastric cancer cells, which can be achieved by inhibiting PHB expression, thus altering the structure and function of mitochondria and activating the mitochondria apoptosis pathway. The antitumor effect of COE has also been proved in vivo.

Prevention of acquired sensorineural hearing loss in mice by in vivo Htra2 gene editing

BACKGROUND

Aging, noise, infection, and ototoxic drugs are the major causes of human acquired sensorineural hearing loss, but treatment options are limited. CRISPR/Cas9 technology has tremendous potential to become a new therapeutic modality for acquired non-inherited sensorineural hearing loss. Here, we develop CRISPR/Cas9 strategies to prevent aminoglycoside-induced deafness, a common type of acquired non-inherited sensorineural hearing loss, via disrupting the Htra2 gene in the inner ear which is involved in apoptosis but has not been investigated in cochlear hair cell protection.

RESULTS

The results indicate that adeno-associated virus (AAV)-mediated delivery of CRISPR/SpCas9 system ameliorates neomycin-induced apoptosis, promotes hair cell survival, and significantly improves hearing function in neomycin-treated mice. The protective effect of the AAV-CRISPR/Cas9 system in vivo is sustained up to 8 weeks after neomycin exposure. For more efficient delivery of the whole CRISPR/Cas9 system, we also explore the AAV-CRISPR/SaCas9 system to prevent neomycin-induced deafness. The in vivo editing efficiency of the SaCas9 system is 1.73% on average. We observed significant improvement in auditory brainstem response thresholds in the injected ears compared with the non-injected ears. At 4 weeks after neomycin exposure, the protective effect of the AAV-CRISPR/SaCas9 system is still obvious, with the improvement in auditory brainstem response threshold up to 50 dB at 8 kHz.

CONCLUSIONS

These findings demonstrate the safe and effective prevention of aminoglycoside-induced deafness via Htra2 gene editing and support further development of the CRISPR/Cas9 technology in the treatment of non-inherited hearing loss as well as other non-inherited diseases.

A High-Density Human Mitochondrial Proximity Interaction Network

We used BioID, a proximity-dependent biotinylation assay with 100 mitochondrial baits from all mitochondrial sub-compartments, to create a high-resolution human mitochondrial proximity interaction network. We identified 1,465 proteins, producing 15,626 unique high-confidence proximity interactions. Of these, 528 proteins were previously annotated as mitochondrial, nearly half of the mitochondrial proteome defined by Mitocarta 2.0. Bait-bait analysis showed a clear separation of mitochondrial compartments, and correlation analysis among preys across all baits allowed us to identify functional clusters involved in diverse mitochondrial functions and to assign uncharacterized proteins to specific modules. We demonstrate that this analysis can assign isoforms of the same mitochondrial protein to different mitochondrial sub-compartments and show that some proteins may have multiple cellular locations. Outer membrane baits showed specific proximity interactions with cytosolic proteins and proteins in other organellar membranes, suggesting specialization of proteins responsible for contact site formation between mitochondria and individual organelles.

Prohibitin 1 (PHB1) controls growth and development and regulates proliferation and apoptosis in Schistosoma japonicum

Schistosomiasis is a zoonotic parasitic disease caused by the trematode blood flukes of the genus Schistosoma. The prodigious egg output of females is the main cause of the disease in definitive hosts, while the female worm relies on continuous pairing with the male worm to fuel the growth and maturation of the reproductive organs and egg production. Prohibitin, which contains the functionally interdependent PHB1 and PHB2 subunits in human and some other species, has been proposed to participate in the cell proliferation and apoptosis regulation in mammals. However, little is known about the function of PHB homolog in the growth and reproductive development of schistosomes. Here, we reported the Phb1 gene that was structurally and evolutionarily conserved in Schistosoma japonicum when compared with that of other species from Caenorhabditis elegans to human. Real-time PCR detected that SjPhb1 was highly transcribed in the vitellaria of female worms. SjPhb1 knockdown achieved through the dsRNA-mediated RNAi in vivo resulted in retarded growth, decreased pairing, and fecundity in adult worms, as well as attenuated pathogenicity or virulence of worms to their hosts. Cell proliferation and apoptosis examination found decreased cell proliferation and increased cell apoptosis in SjPhb1 dsRNA-treated worms. Therefore, our study provides the first characterization of S. japonicum PHB1 and reveals its fundamental role in the regulation of growth and development of S. japonicum by specific dsRNA-mediated RNAi in vivo. Our findings prompt for a promising molecular of schistosomes that can be targeted to effectively retard the growth and development of the schistosomes.

A novel prognostic marker and immunogenic membrane antigen: prohibitin (PHB) in pancreatic cancer

Background

Previous study, using immunoblotting with IgG and membrane proteins, identified prohibitin (PHB) as a potential immunogenic membrane antigen. Now, investigate PHB expression and biological functions in pancreatic cancer.

Methods

PHB expression was analysed in PDAC cell lines, normal pancreas tissues, cancer tissues, PDAC patient sera and healthy volunteer sera using QRT-PCR, Western blotting, IHC, and ELISA, and a survival analysis and a COX regression analysis were performed. Low and high PHB expression levels were accomplished using RNA interference technology and gene transfer techniques. Cell proliferation, migration, and invasion, apoptosis-related proteins were assessed 48 h after transfection.

Results

PHB was generally expressed in the 8 tested PDAC cell lines. PHB was significantly increased in PDAC tissues and negatively correlated with overall survival (p < 0.01). PHB was an independent prognostic factor in PDAC (p < 0.01). PHB was increased in PDAC patient sera (p < 0.01). siRNA-PHB decreased cell growth, migration and invasion. However, PHB overexpression resulted in the opposite effects. Western blotting and Flow cytometric analysis revealed apoptosis inhibition in siRNA-PHB PDAC cells.

Conclusions

PHB plays a key role in modulating the malignant phenotype and apoptosis induction, which may be a novel prognostic predictor and a candidate for targeted therapy against PDAC.