Prohibitin 2/PHB2 in Parkin-Mediated Mitophagy: A Potential Therapeutic Target for Non-Small Cell Lung Carcinoma

Identification of circular RNAs regulating cardiomyocyte proliferation in neonatal pig hearts

Little is known about the expression patterns and functions of circular RNAs (circRNAs) in the heart of large mammals. In this study, we examined the expression profiles of circRNAs, microRNAs (miRNAs), and messenger RNAs (mRNAs) in neonatal pig hearts. Pig heart samples collected on postnatal days 1 (P1), 3 (P3), 7 (P7), and 28 (P28) were sent for total RNA sequencing. Our data revealed a total of 7,000 circRNAs in the 24 pig hearts. Pathway enrichment analysis of hallmark gene sets demonstrated that differentially expressed circRNAs were engaged in different pathways. The most significant difference was observed between P1 and the other 3 groups (P3, P7, and P28) in pathways related to cell cycle and muscle development. Out of the 10 circRNAs that were validated through real-time quantitative PCR to verify their expression, 6 exhibited significant effects on cell cycle activity in human induced pluripotent stem cell-derived cardiomyocytes following small interfering RNA-mediated knockdown. circRNA-miRNA-mRNA networks were constructed to understand the potential mechanisms of circRNAs in the heart. In conclusion, our study provided a data set for exploring the roles of circRNAs in pig hearts. In addition, we identified several circRNAs that regulate cardiomyocyte cell cycle.

Insights into the role of mitophagy in lung cancer: current evidence and perspectives

Lung cancer, recognized globally as a leading cause of malignancy-associated morbidity and mortality, is marked by its high prevalence and lethality, garnering extensive attention within the medical community. Mitophagy is a critical cellular process that plays a crucial role in regulating metabolism and ensuring quality control within cells. Its relevance to lung cancer has garnered significant attention among researchers and scientists. Mitophagy's involvement in lung cancer encompasses its initiation, progression, metastatic dissemination and treatment. The regulatory landscape of mitophagy is complex, involving numerous signaling proteins and pathways that may exhibit aberrant alterations or mutations within the tumor environment. In the field of treatment, the regulation of mitophagy is considered key to determining cancer chemotherapy, radiation therapy, other treatment options, and drug resistance. Contemporary investigations are directed towards harnessing mitophagy modulators, both inhibitors and activators, in therapeutic strategies, with an emphasis on achieving specificity to minimize collateral damage to healthy cellular populations. Furthermore, molecular constituents and pathways affiliated with mitophagy, serving as potential biomarkers, offer promising avenues for enhancing diagnostic accuracy, prognostic assessment, and prediction of therapeutic responses in lung cancer. Future endeavors will also involve investigating the impact of mitophagy on the composition and function of immune cells within the tumor microenvironment, aiming to enhance our understanding of how mitophagy modulates the immune response to lung cancer. This review aims to comprehensively overview recent advancements about the role of mitophagy in the tumor genesis, progenesis and metastasis, and the impact of mitophagy on the treatment of lung cancer. We also discussed the future research direction of mitophagy in the field of lung cancer.

Biomarkers in Thyroid Cancer: Emerging Opportunities from Non-Coding RNAs and Mitochondrial Space

Thyroid cancer diagnosis primarily relies on imaging techniques and cytological analyses. In cases where the diagnosis is uncertain, the quantification of molecular markers has been incorporated after cytological examination. This approach helps physicians to make surgical decisions, estimate cancer aggressiveness, and monitor the response to treatments. Despite the availability of commercial molecular tests, their widespread use has been hindered in our experience due to cost constraints and variability between them. Thus, numerous groups are currently evaluating new molecular markers that ultimately will lead to improved diagnostic certainty, as well as better classification of prognosis and recurrence. In this review, we start reviewing the current preoperative testing methodologies, followed by a comprehensive review of emerging molecular markers. We focus on micro RNAs, long non-coding RNAs, and mitochondrial (mt) signatures, including mtDNA genes and circulating cell-free mtDNA. We envision that a robust set of molecular markers will complement the national and international clinical guides for proper assessment of the disease.

Prohibitin 2: A key regulator of cell function

The PHB2 gene is located on chromosome 12p13 and encodes prohibitin 2, a highly conserved protein of 37 kDa. PHB2 is a dimer with antiparallel coils, possessing a unique negatively charged region crucial for its mitochondrial molecular chaperone functions. Thus, PHB2 plays a significant role in cell life activities such as mitosis, mitochondrial autophagy, signal transduction, and cell death. This review discusses how PHB2 inhibits transcription factors or nuclear receptors to maintain normal cell functions; how PHB2 in the cytoplasm or membrane ensures normal cell mitosis and regulates cell differentiation; how PHB2 affects mitochondrial structure, function, and cell apoptosis through mitochondrial intimal integrity and mitochondrial autophagy; how PHB2 affects mitochondrial stress and inhibits cell apoptosis by regulating cytochrome c migration and other pathways; how PHB2 affects cell growth, proliferation, and metastasis through a mitochondrial independent mechanism; and how PHB2 could be applied in disease treatment. We provide a theoretical basis and an innovative perspective for a comprehensive understanding of the role and mechanism of PHB2 in cell function regulation.

Resveratrol augments paclitaxel sensitivity by modulating miR-671-5p/STOML2/PINK1/Parkin-mediated autophagy signaling in A549 cell

BACKGROUND

Paclitaxel (PTX) resistance has become a notable clinical concern of Non-small cell lung cancer (NSCLC). Our study aim is to investigate the effects of Resveratrol (RES) on NSCLC cells that have developed resistance to PTX. The NSCLC cell line A549 was employed in this investigation to establish a PTX-resistant NSCLC cell line, denoted as A549/PTX, and established tumor transplantaton model. The presence of miR-671-5p, Stomatin-like protein 2 (STOML2), and mitophagy biomarkers was evaluated using quantitative teal-time PCR (qRT-PCR) and western blot, The assessment of cell proliferation and apoptosis was conducted through the utilisation of colony formation and flow cytometry assays. The investigation of mitochondrial autolysosomes was conducted using transmission electron microscopy (TEM). Our results showed that the application of RES therapy resulted in a substantial improvement in the sansitivity of A549/PTX cells. RES exhibited an augmentation of apoptosis and a suppression of mitophagy in A549/PTX cells. RES induced an upregulation in the expression of miR-671-5p. This, in turn, leaded to the inhibition of STOML2, a protein that directly interacts with PINK1. In summary, our research indicates that RES improved the susceptibility of A549/PTX cells to PTX through miR-671-5p-mediated STOML2 inhibition.

Prohibitin2/PHB2, Transcriptionally Regulated by GABPA, Inhibits Cell Growth via PRKN/Parkin-dependent Mitophagy in Endometriosis

Endometriosis (EMS) is a common benign gynecological disease affecting women of reproductive age. It is characterized by abnormal growth of endometrial tissue outside the uterine cavity, resulting in chronic pelvic pain and infertility. Endometrial physiological and pathological processes are intimately connected to autophagy. Mitophagy is an essential selective mode that protects cells from metabolic stress and hypoxia. Mitochondrial autophagy mediated by prohibitin 2 (PHB2) is dependent on the PRKN/Parkin pathway and is involved in numerous human diseases. Uncertainty remains as to whether mitophagy regulation by PHB2 contributes to the occurrence and progression of EMS. This study aims to investigate the mechanism underlying the role of PHB2 in EMS. This study detected the protein and mRNA expression of PHB2 in ectopic and normal endometrial tissues of ovarian EMS, in addition to ectopic endometrial cell line 12Z and endometrial stromal cell line KC02-44D for gene overexpression or knockdown. Cell function experiments and mitochondrial function experiments were conducted to investigate the role of PHB2 in the endometrium. Bioinformatic analysis and experiments were also used to investigate the upstream transcription factors that influence PHB2 expression. PHB2 was downregulated in ectopic endometrium, and PHB2 overexpression inhibited cell proliferation, migration, and invasion and promoted apoptosis. The upregulation of mitophagy markers, including Parkin and LC3II/I, and the downregulation of autophagy degradation markers P62 and TOMM20 in EMS suggest that PHB2 may contribute to cell proliferation, migration, invasion, and apoptosis via PRKN/Parkin-mediated mitophagy. Analysis and validation of bioinformatics data revealed that the transcription factor GABPA binds directly to the PHB2 promoter region and controls the transcriptional expression of PHB2. This study investigated the role of PHB2 in the onset of EMS. It inhibits EMS growth via PRKN/Parkin-mediated mitophagy, and GABPA controls the transcriptional disorder of PHB2. This study's findings suggest a novel method for investigating the clinical potential of PHB2 in EMS.

PHB2 Alleviates Neurotoxicity of Prion Peptide PrP106-126 via PINK1/Parkin-Dependent Mitophagy

Prion diseases are a group of neurodegenerative diseases characterized by mitochondrial dysfunction and neuronal death. Mitophagy is a selective form of macroautophagy that clears injured mitochondria. Prohibitin 2 (PHB2) has been identified as a novel inner membrane mitophagy receptor that mediates mitophagy. However, the role of PHB2 in prion diseases remains unclear. In this study, we isolated primary cortical neurons from rats and used the neurotoxic prion peptide PrP106-126 as a cell model for prion diseases. We examined the role of PHB2 in PrP106-126-induced mitophagy using Western blotting and immunofluorescence microscopy and assessed the function of PHB2 in PrP106-126-induced neuronal death using the cell viability assay and the TUNEL assay. The results showed that PrP106-126 induced mitochondrial morphological abnormalities and mitophagy in primary cortical neurons. PHB2 was found to be indispensable for PrP106-126-induced mitophagy and was involved in the accumulation of PINK1 and recruitment of Parkin to mitochondria in primary neurons. Additionally, PHB2 depletion exacerbated neuronal cell death induced by PrP106-126, whereas the overexpression of PHB2 alleviated PrP106-126 neuronal toxicity. Taken together, this study demonstrated that PHB2 is indispensable for PINK1/Parkin-mediated mitophagy in PrP106-126-treated neurons and protects neurons against the neurotoxicity of the prion peptide.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Essential Protein PHB2 and Its Regulatory Mechanisms in Cancer

Prohibitins (PHBs) are a highly conserved class of proteins and have an essential role in transcription, epigenetic regulation, nuclear signaling, mitochondrial structural integrity, cell division, and cellular membrane metabolism. Prohibitins form a heterodimeric complex, consisting of two proteins, prohibitin 1 (PHB1) and prohibitin 2 (PHB2). They have been discovered to have crucial roles in regulating cancer and other metabolic diseases, functioning both together and independently. As there have been many previously published reviews on PHB1, this review focuses on the lesser studied prohibitin, PHB2. The role of PHB2 in cancer is controversial. In most human cancers, overexpressed PHB2 enhances tumor progression, while in some cancers, it suppresses tumor progression. In this review, we focus on (1) the history, family, and structure of prohibitins, (2) the essential location-dependent functions of PHB2, (3) dysfunction in cancer, and (4) the promising modulators to target PHB2. At the end, we discuss future directions and the clinical significance of this common essential gene in cancer.

Tetrahydroberberrubine retards heart aging in mice by promoting PHB2-mediated mitophagy

Heart aging is characterized by left ventricular hypertrophy and diastolic dysfunction, which in turn induces a variety of cardiovascular diseases. There is still no therapeutic drug to ameliorate cardiac abnormities in heart aging. In this study we investigated the protective effects of berberine (BBR) and its derivative tetrahydroberberrubine (THBru) against heart aging process. Heart aging was induced in mice by injection of D-galactose (D-gal, 120 mg · kg-1 · d-1, sc.) for 12 weeks. Meanwhile the mice were orally treated with berberine (50 mg · kg-1 · d-1) or THBru (25, 50 mg · kg-1 · d-1) for 12 weeks. We showed that BBR and THBru treatment significantly mitigated diastolic dysfunction and cardiac remodeling in D-gal-induced aging mice. Furthermore, treatment with BBR (40 μM) and THBru (20, 40 μM) inhibited D-gal-induced senescence in primary neonatal mouse cardiomyocytes in vitro. Overall, THBru exhibited higher efficacy than BBR at the same dose. We found that the levels of mitophagy were significantly decreased during the aging process in vivo and in vitro, THBru and BBR promoted mitophagy with different potencies. We demonstrated that the mitophagy-inducing effects of THBru resulted from increased mRNA stability of prohibitin 2 (PHB2), a pivotal factor during mitophagy, thereby upregulating PHB2 protein expression. Knockdown of PHB2 effectively reversed the antisenescence effects of THBru in D-gal-treated cardiomyocytes. On the contrary, overexpression of PHB2 promoted mitophagy and retarded cardiomyocyte senescence, as THBru did. In conclusion, this study identifies THBru as a potent antiaging medicine that induces PHB2-mediated mitophagy and suggests its clinical application prospects.

Resveratrol regulates PINK1/Parkin-mediated mitophagy via the lncRNA ZFAS1-miR-150-5p-PINK1 axis, and enhances the antitumor activity of paclitaxel against non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a common malignant subtype of lung cancer with high mortality. Resveratrol (RSV) is a natural molecule that regulates mitochondrial metabolism. Here, we explored the effect of RSV on NSCLC cell mitophagy and paclitaxel (PTX) resistance. LncRNA ZFAS1, miR-150-5p, and PTEN-induced putative kinase 1 (PINK1) expressions in NSCLC cells were analyzed by RT-qPCR. Levels of PINK1, Parkin and autophagy related molecules LC3I and LC3II were assessed by western blot. Mitophagy was demonstrated by transmission electron microscopy. Luciferase reporter assay revealed that miR-150-5p directly interacted with ZFAS1 or PINK1. MTT was performed to test the IC50 of NSCLC cells. Cell proliferation and apoptosis were measured with CCK-8, EdU, and TUNEL assays. A549/PTX cells exhibited a higher mitophagy activity, and chemoresistance, whereas RSV suppressed PTX resistance and mitophagy in NSCLC cells. Furthermore, ZFAS1 was found to be a downstream effector of RSV in NSCLC cells. We next found ZFAS1 directly interacted with miR-150-5p and regulated the expression of a key mitophagy regulator PINK1. In addition, RSV modulated PTX resistance and mitophagy in NSCLC via ZFAS1/miR-150-5p/PINK1 axis. We validate that RSV influences mitophagy and PTX resistance in NSCLC via ZFAS1/miR-150-5p mediated PINK1/Parkin pathway. Combining these 2 drugs may be a new option of NSCLC therapy.

Nonreceptor Tyrosine Kinase c-Abl-Mediated PHB2 Phosphorylation Aggravates Mitophagy Disorder in Parkinson’s Disease Model

Mitophagy and oxidative stress play important roles in Parkinson's disease (PD). Dysregulated mitophagy exacerbates mitochondrial oxidative damage; however, the regulatory mechanism of mitophagy is unclear. Here, we provide a potential mechanistic link between c-Abl, a nonreceptor tyrosine kinase, and mitophagy in PD progression. We found that c-Abl activation reduces the interaction of prohibitin 2 (PHB2) and microtubule-associated protein 1 light chain 3 (LC3) and decreases the expressive level of antioxidative stress proteins, including nuclear factor erythroid 2-related factor 2 (Nrf2), NADPH quinone oxidoreductase-1 (NQO-1), and the antioxidant enzyme heme oxygenase-1 (HO-1) in 1-methyl-4-phenylpyridinium- (MPP⁺-) lesioned SH-SY5Y cells. Importantly, we found that MPP⁺ can increase the expression of phosphorylated proteins at the tyrosine site of PHB2 and the interaction of c-Abl with PHB2. We showed for the first time that PHB2 by changing tyrosine (Y) to aspartate (D) at site 121 resulted in impaired binding of PHB2 and LC3 in vitro. Moreover, silencing of PHB2 can decrease the interaction of PHB2 and LC3 and exacerbate the loss of dopaminergic neurons. We also found that STI 571, a c-Abl family kinase inhibitor, can decrease dopaminergic neuron damage and ameliorate MPTP-induced behavioral deficits in PD mice. Taken together, our findings highlight a novel molecular mechanism for aberrant PHB2 phosphorylation as an inhibitor of c-Abl activity and suggest that c-Abl and PHB2 are potential therapeutic targets for the treatment of individuals with PD. However, these results need to be further validated in PHB2 Y121D mice.

Development and validation of a novel mitophagy-related gene prognostic signature for glioblastoma multiforme

Background

Glioblastoma multiforme (GBM) is one of the most malignant tumors in brain with high morbidity and mortality. Mitophagy plays a significant role in carcinogenesis, metastasis, and invasion. In our study, we aim to construct a mitophagy-related risk model to predict prognosis in GBM.

Methods

RNA-seq data combined with clinical information were downloaded from TCGA. The 4-gene risk model and nomograph was then constructed and validated in external cohort. Evaluation of immune infiltration, functional enrichment and tumor microenvironment (TME) were then performed.

Result

A mitophagy-related risk model was established and patients in TCGA and CGGA were classified into low-risk and high-risk groups. In both cohorts, patients in low-risk group had improved survival, while high-risk group had poor prognosis. Also, the risk model was identified as an independent factor for predicting overall survival via Cox regression. Furthermore, a prognostic nomogram including mitophagy signatures was established with excellent predictive performance. In addition, the risk model was closely associated with regulation of immune infiltration as well as TME.

Conclusion

In conclusion, our study constructed a mitophagy-related risk model, which can be utilized for the clinical prognostic prediction in GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09707-w.

Src Activation Aggravates Podocyte Injury in Diabetic Nephropathy via Suppression of FUNDC1-Mediated Mitophagy

Background and purpose: Mitophagy plays a significant role in the progression of diabetic nephropathy (DN), although the regulatory mechanisms remain unclear. Recently, accumulating evidence demonstrated that impaired mitochondrial function and mitophagy are involved in DN. Here, we are aimed to explore the role of c-Src (Src) and FUNDC1-related mitophagy in the development of DN.

Methods: The db/db mice were used to establish a DN mice model. The mice accepted PP2 (Src inhibitor) treatment to study the role of Src in DN. Kidney function was measured via biochemical testing. Renal histopathology and morphometric analysis were conducted via hematoxylin-eosin (HE), periodic acid-Schiff (PAS), Masson’s staining, and transmission electron microscopy (TEM). We measured degree of apoptosis in kidney by TUNEL assay. Indices of mitophagy (LC3 and p62) were evaluated by Western blotting and immunofluorescence. Complementary in vitro assays were conducted using human podocytes subjected to high glucose in combination with PP2 treatment or FUNDC1 small interfering RNAs (siRNAs). Flow cytometry was used to detect the apoptotic cells. Mitochondrial function was evaluated by JC-1 staining. Double immunofluorescence labeling of LC3 and TOMM20 used to assess the degree of mitophagy.

Results: Increased Src activation was detected in the kidneys of db/db mice, and its expression was positively correlated with mitochondrial damage, podocyte apoptosis, and renal dysfunction. Inhibition of Src activation with PP2 protected against mitochondrial damage and podocyte apoptosis. In vitro experiments in podocytes established that high glucose increased Src activation, promoting FUNDC1 phosphorylation and inhibiting mitophagy. Consistent with the mouse model, inhibiting Src activity protected podocytes against mitochondrial damage. FUNDC1 silencing negated the actions of PP2, indicating that FUNDC1-mediated mitophagy is downstream pathway of Src.

Conclusion: In summary, our data indicated that Src is a culprit factor in diabetic renal damage via suppression of FUNDC1-mediated mitophagy, promoting the development of DN.

The expression of PHB2 in the cochlea: Possible relation to age-related hearing loss

Age-related hearing loss (ARHL) is the most prevalent sensory deficit in the elderly, but its mechanism remains unclear. Scaffold protein prohibitin 2 (PHB2) has been widely involved in aging and neurodegeneration. However, the role of PHB2 in ARHL is undeciphered to date. To investigate the expression pattern and the role of PHB2 in ARHL, we used C57BL/6 mice and HEI-OC1 cell line as models. In our study, we have found PHB2 exists in the cochlea and is expressed in hair cells, spiral ganglion neurons, and HEI-OC1 cells. In mice with ARHL, mitophagy is reduced and correspondingly the expression level of PHB2 is decreased. Moreover, after H₂ O₂ treatment the mitophagy is activated and the PHB2 expression is increased. These findings indicate that PHB2 may exert an important role in ARHL through mitophagy. Findings from this study will be helpful for elucidating the mechanism underlying the ARHL and for providing a new target for ARHL treatment.

PHB2 promotes tumorigenesis via RACK1 in non-small cell lung cancer

Background: Lung cancer has the highest mortality rate among cancers worldwide, with non-small cell lung cancer (NSCLC) the most common type. Increasing evidence shows that PHB2 is highly expressed in other cancer types; however, the effects of PHB2 in NSCLC are currently poorly understood.

Method: PHB2 expression and its clinical relevance in NSCLC tumor tissues were analyzed using a tissue microarray. The biological role of PHB2 in NSCLC was investigated in vitro and in vivo using immunohistochemistry and immunofluorescence staining, gene expression knockdown and overexpression, cell proliferation assay, flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, wound healing assay, Transwell assay, western blot analysis, qRT-PCR, coimmunoprecipitation, and mass spectrometry analysis.

Results: Our major finding is that PHB2 facilitates tumorigenesis in NSCLC by interacting with and stabilizing RACK1, which further induces activation of downstream tumor-promoting effectors. PHB2 was found to be overexpressed in NSCLC tumor tissues, and its expression was correlated with clinicopathological features. Furthermore, PHB2 overexpression promoted proliferation, migration, and invasion, whereas PHB2 knockdown enhanced apoptosis in NSCLC cells. The stimulating effect of PHB2 on tumorigenesis was also verified in vivo. In addition, PHB2 interacted with RACK1 and increased its expression through posttranslational modification, which further induced activation of the Akt and FAK pathways.

Conclusions: Our results reveal the effects of PHB2 on tumorigenesis and its regulation of RACK1 and RACK1-associated proteins and downstream signaling in NSCLC. We believe that the crosstalk between PHB2 and RACK1 provides us with a great opportunity to design and develop novel therapeutic strategies for NSCLC.

Mitophagy Receptors in Tumor Biology

Mitochondria are multifunctional organelles that regulate cancer biology by synthesizing macromolecules, producing energy, and regulating cell death. The understanding of mitochondrial morphology, function, biogenesis, fission and fusion kinetics, and degradation is important for the development of new anticancer strategies. Mitophagy is a type of selective autophagy that can degrade damaged mitochondria under various environmental stresses, especially oxidative damage and hypoxia. The key regulator of mitophagy is the autophagy receptor, which recognizes damaged mitochondria and allows them to enter autophagosomes by binding to MAP1LC3 or GABARAP, and then undergo lysosomal-dependent degradation. Many components of mitochondria, including mitochondrial membrane proteins (e.g., PINK1, BNIP3L, BNIP3, FUNDC1, NIPSNAP1, NIPSNAP2, BCL2L13, PHB2, and FKBP8) and lipids (e.g., cardiolipin and ceramides), act as mitophagy receptors in a context-dependent manner. Dysfunctional mitophagy not only inhibits, but also promotes, tumorigenesis. Similarly, mitophagy plays a dual role in chemotherapy, radiotherapy, and immunotherapy. In this review, we summarize the latest advances in the mechanisms of mitophagy and highlight the pathological role of mitophagy receptors in tumorigenesis and treatment.