GOLPH3 inhibits erastin-induced ferroptosis in colorectal cancer cells.

Ferroptosis is a novel form of programmed cell death and is considered to be a druggable target for colorectal cancer (CRC) therapy. However, the role of ferroptosis in CRC and its underlying mechanism are not fully understood. In the present study we found that a protein enriched in the Golgi apparatus, Golgi phosphoprotein 3 (GOLPH3), was overexpressed in human CRC tissue and in several CRC cell lines. The expression of GOLPH3 was significantly correlated with the expression of ferroptosis-related genes in CRC. The overexpression of GOLPH3 in Erastin-induced Caco-2 CRC cells reduced ferroptotic phenotypes, whereas the knockdown of GOLPH3 potentiated ferroptosis in HT-29 CRC cells. GOLPH3 induced the expression of prohibitin-1 (PHB1) and prohibitin-2 (PHB2), which also inhibited ferroptosis in Erastin-treated CRC cells. Moreover, GOLPH3 interacted with PHB2 and nuclear factor erythroid 2-related factor 2 (NRF2) in Caco-2 cells. These observations indicate that GOLPH3 is a negative regulator of ferroptosis in CRC cells. GOLPH3 protects these cells from ferroptosis by inducing the expression of PHB1 and PHB2, and by interacting with PHB2 and NRF2.

Progesterone-induced progesterone receptor membrane component 1 rise-to-decline changes are essential for decidualization.

BACKGROUND: Decidualization of endometrial cells is the prerequisite for embryo implantation and subsequent placenta formation and is induced by rising progesterone levels following ovulation. One of the hormone receptors contributing to endometrial homeostasis is Progesterone Receptor Membrane Component 1 (PGRMC1), a non-classical membrane-bound progesterone receptor with yet unclear function. In this study, we aimed to investigate how PGRMC1 contributes to human decidualization. METHODS: We first analyzed PGRMC1 expression profile during a regular menstrual cycle in RNA-sequencing datasets. To further explore the function of PGRMC1 in human decidualization, we implemented an inducible decidualization system, which is achieved by culturing two human endometrial stromal cell lines in decidualization-inducing medium containing medroxyprogesterone acetate and 8-Br-cAMP. In our system, we measured PGRMC1 expression during hormone induction as well as decidualization status upon PGRMC1 knockdown at different time points. We further conferred proximity ligation assay to identify PGRMC1 interaction partners. RESULTS: In a regular menstrual cycle, PGRMC1 mRNA expression is gradually decreased from the proliferative phase to the secretory phase. In in vitro experiments, we observed that PGRMC1 expression follows a rise-to-decline pattern, in which its expression level initially increased during the first 6 days after induction (PGRMC1 increasing phase) and decreased in the following days (PGRMC1 decreasing phase). Knockdown of PGRMC1 expression before the induction led to a failed decidualization, while its knockdown after induction did not inhibit decidualization, suggesting that the progestin-induced 'PGRMC1 increasing phase' is essential for normal decidualization. Furthermore, we found that the interactions of prohibitin 1 and prohibitin 2 with PGRMC1 were induced upon progestin treatment. Knocking down each of the prohibitins slowed down the decidualization process compared to the control, suggesting that PGRMC1 cooperates with prohibitins to regulate decidualization. CONCLUSIONS: According to our findings, PGRMC1 expression followed a progestin-induced rise-to-decline expression pattern during human endometrial decidualization process; and the correct execution of this expression program was crucial for successful decidualization. Thereby, the results of our in vitro model explained how PGRMC1 dysregulation during decidualization may present a new perspective on infertility-related diseases.

Prohibitin1 facilitates viral replication by impairing the RIG-I-like receptor signaling pathway.

IMPORTANCE: Type I interferon (IFN-I), produced by the innate immune system, plays an essential role in host antiviral responses. Proper regulation of IFN-I production is required for the host to balance immune responses and prevent superfluous inflammation. IFN regulatory factor 3 (IRF3) and subsequent sensors are activated by RNA virus infection to induce IFN-I production. Therefore, proper regulation of IRF3 serves as an important way to control innate immunity and viral replication. Here, we first identified Prohibitin1 (PHB1) as a negative regulator of host IFN-I innate immune responses. Mechanistically, PHB1 inhibited the nucleus import of IRF3 by impairing its binding with importin subunit alpha-1 and importin subunit alpha-5. Our study demonstrates the mechanism by which PHB1 facilitates the replication of multiple RNA viruses and provides insights into the negative regulation of host immune responses.

The landscape of mitophagy in sepsis reveals PHB1 as an NLRP3 inflammasome inhibitor.

Mitophagy is a selective autophagy targeting damaged and potential cytotoxic mitochondria, which can effectively prevent excessive cytotoxic production from damaged mitochondria and alleviate the inflammatory response. However, the potential role of mitophagy in sepsis remains poorly explored. Here, we studied the role of mitophagy in sepsis and its immune heterogeneity. By performing mitophagy-related typing on 348 sepsis samples, three clusters (A, B, and C) were obtained. Cluster A had the highest degree of mitophagy accompanied by lowest disease severity, while cluster C had the lowest degree of mitophagy with the highest disease severity. The three clusters had unique immune characteristics. We further revealed that the expression of PHB1 in these three clusters was significantly different and negatively correlated with the severity of sepsis, suggesting that PHB1 was involved in the development of sepsis. It has been reported that impaired mitophagy leads to the over-activation of inflammasomes, which promotes sepsis development. Further analysis showed that the expressions of NLRP3 inflammasomes core genes in cluster C were significantly up-regulated and negatively correlated with PHB1. Next, we verified whether PHB1 downregulation caused the activation of inflammasomes and found that the PHB1 knockdown increased the levels of mtDNA in the cytoplasm and enhanced the activation of NLRP3 inflammasomes. In addition, mitophagy inhibitor treatment abolished PHB1 knockdown-mediated activation of NLRP3 inflammasomes, suggesting that PHB1 inhibited the activation of inflammasomes through mitophagy. In conclusion, this study reveals that a high degree of mitophagy may predict a good outcome of sepsis, and PHB1 is a key NLRP3 inflammasome regulator via mitophagy in inflammatory diseases such as sepsis.

RNA interference of PHB1 enhances virulence of Vip3Aa to Sf9 cells and Spodoptera frugiperda larvae.

BACKGROUND: In our previous work, we demonstrated that prohibitin 2 (PHB2) on the membrane of Sf9 cells was a receptor for Vip3Aa, and PHB2 in mitochondria contributed to the mitochondrial stability to reduce Vip3Aa toxicity. Prohibitin 1 (PHB1), another prohibitin family member, forms heterodimers with PHB2 to maintain the structure and stability of mitochondria. To explore whether PHB1 impacts the action process of Vip3Aa, we examined the correlation between PHB1 and Vip3Aa virulence. RESULTS: We revealed that PHB1 did not colocalize with Vip3Aa in Sf9 cells. The pulldown and CoIP experiments confirmed that PHB1 interacted with neither Vip3Aa nor scavenger receptor-C (another Vip3Aa receptor). Downregulating phb1 expression in Sf9 cells did not affect the internalization of Vip3Aa but increased Vip3Aa toxicity. Further exploration revealed that the decrease of phb1 expression affected mitochondrial function, leading to increased ROS levels and mitochondrial membrane permeability and decreased mitochondrial membrane potential. The increase of mitochondrial cytochrome c release, caspase-3 activity and genomic DNA fragmentation implied that the apoptotic process was also affected. Finally, we applied RNAi to inhibit phb1 expression in Spodoptera frugiperda larvae. As a result, it significantly increased Vip3Aa virulence. CONCLUSION: We found that PHB1 was not a receptor for Vip3Aa but played an essential role in mitochondria. The downregulation of phb1 expression in Sf9 cells caused instability of mitochondria, and the cells were more prone to apoptosis when challenged with Vip3Aa. The combined use of Vip3Aa and phb1 RNAi showed a synergistic effect against S. frugiperda larvae. © 2023 Society of Chemical Industry.

Prohibitin1 maintains mitochondrial quality in isoproterenol-induced cardiac hypertrophy in H9C2 cells.

BACKGROUND INFORMATION: Various types of stress initially induce a state of cardiac hypertrophy (CH) in the heart. But, persistent escalation of cardiac stress leads to progression from an adaptive physiological to a maladaptive pathological state. So, elucidating molecular mechanisms that can attenuate CH is imperative in developing cardiac therapies. Previously, we showed that Prohibitin1 (PHB1) has a protective role in CH-induced oxidative stress. Nevertheless, it is unclear how PHB1, a mitochondrial protein, has a protective role in CH. Therefore, we hypothesized that PHB1 maintains mitochondrial quality in CH. To test this hypothesis, we used Isoproterenol (ISO) to induce CH in H9C2 cells overexpressing PHB1 and elucidated mitochondrial quality control pathways. RESULTS: We found that overexpressing PHB1 attenuates ISO-induced CH and restores mitochondrial morphology in H9C2 cells. In addition, PHB1 blocks the pro-hypertrophic IGF1R/AKT pathway and restores the mitochondrial membrane polarization in ISO-treated cells. We observed that overexpressing PHB1 promotes mitochondrial biogenesis, improves mitochondrial respiratory capacity, and triggers mitophagy. CONCLUSION: We conclude that PHB1 maintains mitochondrial quality in ISO-induced CH in H9C2 cells. SIGNIFICANCE: Based on our results, we suggest that small molecules that induce PHB1 in cardiac cells may prove beneficial in developing cardiac therapies.

LPLUNC1 reduces glycolysis in nasopharyngeal carcinoma cells through the PHB1-p53/c-Myc axis.

Cancer cells prefer glycolysis to support their proliferation. Our previous studies have shown that the long palate, lung, and nasal epithelial cell clone 1 (LPLUNC1) can upregulate prohibitin 1 (PHB1) expression to inhibit the proliferation of nasopharyngeal carcinoma (NPC) cells. Given that PHB1 is an important regulator of cell energy metabolism, we explored whether and how LPLUNC1 regulated glucose glycolysis in NPC cells. LPLUNC1 or PHB1 overexpression decreased glycolysis and increased oxidative phosphorylation (OXPHOS)-related protein expression in NPC cells, promoting phosphorylated PHB1 nuclear translocation through 14-3-3σ. LPLUNC1 overexpression also increased p53 but decreased c-Myc expression in NPC cells, which were crucial for the decrease in glycolysis and increase in OXPHOS-related protein expression induced by LPLUNC1 overexpression. Finally, we found that treatment with all-trans retinoic acid (ATRA) reduced the viability and clonogenicity of NPC cells, decreased glycolysis, and increased OXPHOS-related protein expression by enhancing LPLUNC1 expression in NPC cells. Therefore, the LPLUNC1-PHB1-p53/c-Myc axis decreased glycolysis in NPC cells, and ATRA upregulated LPLUNC1 expression, ATRA maybe a promising drug for the treatment of NPC.

Prohibitin 1 interacts with p53 in the regulation of mitochondrial dynamics and chemoresistance in gynecologic cancers.

BACKGROUND: Mitochondrial dynamics (e.g. fission/fusion) play an important role in controlling chemoresistance in representative gynecologic malignancies, ovarian and cervical cancer. Processing the long form of Optic atrophy (L-Opa)1 is a distinctive character of mitochondrial fragmentation, associated with chemosensitivity. Here, we examined the role of prohibitin (Phb)1 in increasing L-Opa1 processing via the regulating mitochondrial protease, Oma1 and its direct interaction with p-p53 (ser15) and pro-apoptotic Bcl-2 antagonist/killer (Bak) 1 in the signaling axis and if this phenomenon is associated with prognosis of patients. METHODS: We compared Cisplatin (CDDP)-induced response of mitochondrial dynamics, molecular interaction among p-p53 (ser15)-Phb1-Bak, and chemoresponsiveness in paired chemosensitive and chemoresistant gynecologic cancer cells (ovarian and cervical cancer cell lines) using western blot, immunoprecipitation, sea horse, and immunofluorescence. Translational strategy with proximity ligation assessment in phb1-p-p53 (ser15) in human ovarian tumor sections further confirmed in vitro finding, associated with clinical outcome. RESULTS: We report that: (1) Knock-down of Phb1 prevents Cisplatin (cis-diamine-dichloroplatinum; CDDP) -induced changes in mitochondrial fragmentation and Oma1 mediated cleavage, and Opa1 processing; (2) In response to CDDP, Phb1 facilitates the p-p53 (ser15)-Phb1-Bak interaction in mitochondria in chemosensitive gynecologic cancer cells but not in chemoresistant cells; (3) Akt overexpression results in suppressed p-p53(Ser15)-Phb1 interaction and dysregulated mitochondrial dynamics, and (4) Consistent with in vitro findings, proximity ligation assessment (PLA) in human ovarian tumor sections demonstrated that p-p53(ser15)-Phb1-Bak interaction in mitochondria is associated with better chemoresponsiveness and clinical outcome of patients. Determining the molecular mechanisms by which Phb1 facilitates mitochondrial fragmentation and interacts with p53 may advance the current understanding of chemoresistance and pathogenesis of gynecologic cancer. CONCLUSION: Determining the key molecular mechanisms by which Phb1 facilitates the formation of p-p53 (ser15)-Bak-Phb1 and its involvement in the regulation of mitochondrial dynamics and apoptosis may ultimately contribute to the current understanding of molecular and cellular basis of chemoresistance in this gynecologic cancer.

Upregulation of IRF9 Contributes to Pulmonary Artery Smooth Muscle Cell Proliferation During Pulmonary Arterial Hypertension.

Abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) is a critical pathological feature in the pathogenesis of pulmonary arterial hypertension (PAH), but the regulatory mechanisms remain largely unknown. Herein, we demonstrated that interferon regulatory factor 9 (IRF9) accelerated PASMCs proliferation by regulating Prohibitin 1 (PHB1) expression and the AKT-GSK3ß signaling pathway. Compared with control groups, the rats treated with chronic hypoxia (CH), monocrotaline (MCT) or sugen5416 combined with chronic hypoxia (SuHx), and mice challenged with CH had significantly thickened pulmonary arterioles and hyperproliferative PASMCs. More importantly, the protein level of IRF9 was found to be elevated in the thickened medial wall of the pulmonary arterioles in all of these PAH models. Notably, overexpression of IRF9 significantly promoted the proliferation of rat and human PASMCs, as evidenced by increased cell counts, EdU-positive cells and upregulated biomarkers of cell proliferation. In contrast, knockdown of IRF9 suppressed the proliferation of rat and human PASMCs. Mechanistically, IRF9 directly restrained PHB1 expression and interacted with AKT to inhibit the phosphorylation of AKT at thr308 site, which finally led to mitochondrial dysfunction and PASMC proliferation. Unsurprisingly, MK2206, a specific inhibitor of AKT, partially reversed the PASMC proliferation inhibited by IRF9 knockdown. Thus, our results suggested that elevation of IRF9 facilitates PASMC proliferation by regulating PHB1 expression and AKT signaling pathway to affect mitochondrial function during the development of PAH, which indicated that targeting IRF9 may serve as a novel strategy to delay the pathological progression of PAH.

Role of Prohibitins in Aging and Therapeutic Potential Against Age-Related Diseases.

A decline in mitochondrial function has long been associated with age-related health decline. Several lines of evidence suggest that interventions that stimulate mitochondrial autophagy (mitophagy) can slow aging and prolong healthy lifespan. Prohibitins (PHB1 and PHB2) assemble at the mitochondrial inner membrane and are critical for mitochondrial homeostasis. In addition, prohibitins (PHBs) have diverse roles in cell and organismal biology. Here, we will discuss the role of PHBs in mitophagy, oxidative phosphorylation, cellular senescence, and apoptosis. We will also discuss the role of PHBs in modulating lifespan. In addition, we will review the links between PHBs and diseases of aging. Finally, we will discuss the emerging concept that PHBs may represent an attractive therapeutic target to counteract aging and age-onset disease.

PGRMC1 Promotes Progestin-Dependent Proliferation of Breast Cancer Cells by Binding Prohibitins Resulting in Activation of ERα Signaling.

In previous studies, we reported that progesterone receptor membrane component 1 (PGRMC1) is implicated in progestin signaling and possibly associated with increased breast cancer risk upon combined hormone replacement therapy. To gain mechanistic insight, we searched for potential PGRMC1 interaction partners upon progestin treatment by co-immunoprecipitation and mass spectrometry. The interactions with the identified partners were further characterized with respect to PGRMC1 phosphorylation status and with emphasis on the crosstalk between PGRMC1 and estrogen receptor α (ERα). We report that PGRMC1 overexpression resulted in increased proliferation of hormone receptor positive breast cancer cell lines upon treatment with a subgroup of progestins including norethisterone and dydrogesterone that promote PGRMC1-phosphorylation on S181. The ERα modulators prohibitin-1 (PHB1) and prohibitin-2 (PHB2) interact with PGRMC1 in dependency on S181-phosphorylation upon treatment with the same progestins. Moreover, increased interaction between PGRMC1 and PHBs correlated with decreased binding of PHBs to ERα and subsequent ERα activation. Inhibition of either PGRMC1 or ERα abolished this effect. In summary, we provide strong evidence that activated PGRMC1 associates with PHBs, competitively removing them from ERα, which then can develop its transcriptional activities on target genes. This study emphasizes the role of PGRMC1 in a key breast cancer signaling pathway which may provide a new avenue to target hormone-dependent breast cancer.

Activation of mTORC1 and c-Jun by Prohibitin1 loss in Schwann cells may link mitochondrial dysfunction to demyelination.

Schwann cell (SC) mitochondria are quickly emerging as an important regulator of myelin maintenance in the peripheral nervous system (PNS). However, the mechanisms underlying demyelination in the context of mitochondrial dysfunction in the PNS are incompletely understood. We recently showed that conditional ablation of the mitochondrial protein Prohibitin 1 (PHB1) in SCs causes a severe and fast progressing demyelinating peripheral neuropathy in mice, but the mechanism that causes failure of myelin maintenance remained unknown. Here, we report that mTORC1 and c-Jun are continuously activated in the absence of Phb1, likely as part of the SC response to mitochondrial damage. Moreover, we demonstrate that these pathways are involved in the demyelination process, and that inhibition of mTORC1 using rapamycin partially rescues the demyelinating pathology. Therefore, we propose that mTORC1 and c-Jun may play a critical role as executioners of demyelination in the context of perturbations to SC mitochondria.

HDAC6 promotes sepsis development by impairing PHB1-mediated mitochondrial respiratory chain function.

OBJECTIVE: This study was aimed at investigating the regulation of mitochondrial function by histone deacetylase 6 (HDAC6) and the role of HDAC6 in the development and progression of sepsis. RESULTS: HDAC6 downregulated PHB1 and subsequently promoted the development of CLP-induced sepsis. Inhibition of HDAC6 significantly attenuated CLP-induced sepsis through inhibition of mitochondrial dysfunction and reduced oxidant production, thus protecting the rats from oxidative injury. CONCLUSIONS: In this sepsis model, HDAC6 inhibits the expression and function of PHB1 and alters the function of the mitochondrial respiratory chain mediated by PHB1, thus enhancing the production of oxidants and increasing oxidative stress and thereby leading to severe oxidative injury in multiple organs. METHODS: The expression of HDAC6 and prohibitin 1 (PHB1) in humans and in a rat model of sepsis was measured by quantitative reverse-transcription PCR and western blotting. Sepsis induction by cecal ligation and puncture (CLP) was confirmed by histological analysis. Concentrations of different sepsis markers were measured by an enzyme-linked immunosorbent assay, and mitochondrial function was assessed via the mitochondrial respiratory control rate.

Glucose starvation-induced oxidative stress causes mitochondrial dysfunction and apoptosis via Prohibitin 1 upregulation in human breast cancer cells.

In recent years there has been an upsurge in research focusing on reprogramming cancer cells through understanding of their metabolic signatures. Alterations in mitochondrial bioenergetics and impaired mitochondrial function may serve as effective targeting strategies especially in triple-negative breast cancers (TNBCs) where hormone receptors and endocrine therapy are absent. Glucose starvation (GS) of MDA-MB-231 and MCF-7 breast cancer cells showed decrease in mitochondrial Oxygen Consumption Rate (OCR), which was rescuable to control level through addition of exogenous antioxidant N-Acetyl Cysteine (NAC). Mechanistically, GS led to increase in mitochondrial ROS and upregulation of the pleiotropic protein, Prohibitin 1 (PHB1), leading to its dissociation from Dynamin-related protein 1 (DRP1), perturbance of mitochondrial membrane potential (MMP) and triggering of the apoptosis cascade. PHB1 also reduced the invasive and migratory potential of both cell lines. We emphasize that glucose starvation remarkably sensitized the highly glycolytic metastatic TNBC cell line, MDA-MB-231 to apoptosis and decreased its migratory potential. Based on our findings, additional TNBC cell lines can be evaluated and a nutritional paradigm be proposed for anticancer therapy.

Can Prohibitin 1 be a Safeguard against liver disease?

Prohibitin (PHB) 1 is involved in multiple regulatory pathways in liver disease to protect hepatocytes, and its function is associated with subcellular localization. PHB1 located in the nucleus, cytoplasm and the mitochondrial inner membrane has anti-oxidative stress and anti-inflammatory effects in hepatitis and cirrhosis, which can protect liver cells from damage caused by inflammatory factors and reactive oxygen species (ROS) stimulation. The low expression of PHB1 located in the nucleus of liver cancer cells inhibits the proliferation and metastasis of liver cancer; thus, PHB1 exhibits the function of a tumor suppressor gene. Understanding the mechanisms of PHB1 in liver diseases may be useful for further research on the disease and may provide new ideas for the development of targeted therapeutic drugs in the future. Therefore, this review puts forward an overview of the role of PHB1 and its protective mechanism in liver diseases.

FoxM1 Induced Paclitaxel Resistance via Activation of the FoxM1/PHB1/RAF-MEK-ERK Pathway and Enhancement of the ABCA2 Transporter.

FoxM1 amplification in human pancreatic cancer predicts poor prognosis and resistance to paclitaxel. Here, a novel role between FoxM1 (FoxM1b and FoxM1c) and Prohibitin1 (PHB1) in paclitaxel resistance has been identified. We adopted a bioinformatics approach to predict the potential effector of FoxM1. It specifically bound to the promoter of PHB1, and it enhanced PHB1 expression at transcriptional and post-transcriptional levels. FoxM1 contributed to the PHB1/C-RAF interaction and phosphorylation of ERK1/2 kinases, thus promoting paclitaxel resistance. Notably, FoxM1 conferred tumor cell resistance to paclitaxel, but knocking down PHB1 could sensitize pancreatic cancer cells to it. Besides, we identified that ABCA2 promoted paclitaxel resistance under the regulation of FoxM1/PHB1/RAF-MEK-ERK. Thiostrepton, an inhibitor of FoxM1, significantly decreased the expression of PHB1, p-ERK1/2, and ABCA2. It increased the influx of paclitaxel into the cell, and it attenuated FoxM1-mediated paclitaxel resistance in vitro and in vivo. Collectively, our findings defined PHB1 as an important downstream effector of FoxM1. It was regulated by FoxM1 to maintain phosphorylation of ERK1/2 in drug-resistant cells, and FoxM1 simultaneously enhanced the function of ABCA2, which collectively contributed to paclitaxel resistance. Targeting FoxM1 and its downstream effector PHB1 increased the sensitivity of pancreatic cells to paclitaxel treatment, providing potential therapeutic strategies for patients with paclitaxel resistance.

Profiling and targeting of cellular mitochondrial bioenergetics: inhibition of human gastric cancer cell growth by carnosine.

L-Carnosine (ß-alanyl-L-histidine) is a naturally occurring dipeptide distributed in various organs of mammalians. We previously showed that carnosine inhibited proliferation of human gastric cancer cells through targeting both mitochondrial bioenergetics and glycolysis pathway. But the mechanism underlying carnosine action on mitochondrial bioenergetics of tumor cells remains unclear. In the current study we investigated the effect of carnosine on the growth of human gastric cancer SGC-7901 cells in vitro and in vivo. We firstly showed that hydrolysis of carnosine was not a prerequisite for its anti-gastric cancer effect. Treatment of SGC-7901 cells with carnosine (20 mmol/L) significantly decreased the activities of mitochondrial respiratory chain complexes I-IV and mitochondrial ATP production, and downregulated 13 proteins involved in mitochondrial bioenergetics. Furthermore, carnosine treatment significantly suppressed the phosphorylation of Akt, while inhibition of Akt activation with GSK690693 significantly reduced the localization of prohibitin-1 (PHB-1) in the mitochondria of SGC-7901 and BGC-823 cells. In addition, we showed that silencing of PHB-1 gene with shRNA markedly reduced the mitochondrial PHB-1 in SGC-7901 cells, and significantly decreased the colony formation capacity and growth rate of the cells. In SGC-7901 cell xenograft nude mice, administration of carnosine (250 mg kg/d, ip, for 3 weeks) significantly inhibited the tumor growth and decreased the expression of mitochondrial PHB-1 in tumor tissue. Taken together, these results suggest that carnosine may act on multiple mitochondrial proteins to down-regulate mitochondrial bioenergetics and then to inhibit the growth and proliferation of SGC-7901 and BGC-823 cells.

Mitochondrial Quality Control Mechanisms and the PHB (Prohibitin) Complex.

Mitochondrial functions are essential for life, critical for development, maintenance of stem cells, adaptation to physiological changes, responses to stress, and aging. The complexity of mitochondrial biogenesis requires coordinated nuclear and mitochondrial gene expression, owing to the need of stoichiometrically assemble the oxidative phosphorylation (OXPHOS) system for ATP production. It requires, in addition, the import of a large number of proteins from the cytosol to keep optimal mitochondrial function and metabolism. Moreover, mitochondria require lipid supply for membrane biogenesis, while it is itself essential for the synthesis of membrane lipids. To achieve mitochondrial homeostasis, multiple mechanisms of quality control have evolved to ensure that mitochondrial function meets cell, tissue, and organismal demands. Herein, we give an overview of mitochondrial mechanisms that are activated in response to stress, including mitochondrial dynamics, mitophagy and the mitochondrial unfolded protein response (UPRmt). We then discuss the role of these stress responses in aging, with particular focus on Caenorhabditis elegans. Finally, we review observations that point to the mitochondrial prohibitin (PHB) complex as a key player in mitochondrial homeostasis, being essential for mitochondrial biogenesis and degradation, and responding to mitochondrial stress. Understanding how mitochondria responds to stress and how such responses are regulated is pivotal to combat aging and disease.

[Effects of exhaustive exercise on the expression of PHB1 and the function of mitochondria in rats].

OBJECTIVE: To observe the changes of Prohibitin1(PHB1) contents in rat brain, heart, skeletal muscle tissue and mitochondria with acute exhaustive exercise and the effects of acute exhaustive exercise on mitochondrial function in rats, to explore the relationship among PHB1 and mitochondrial function and energy metabolism. METHODS: Acute exhaustive exercise model:The rats carried acute exhaustive exercise after 8 weeks of feeding. The heart, brain and skeletal muscle samples were collected and the mitochondria were collected to detect the changes of respiratory function and reactive oxygen species(ROS). The expression of PHB1 protein in tissues and mitochondria was detected by Western blot. The ATP content in the organs and the activity of complexes (ATP synthase activity) in mitochondria were measured by spectrophotometer. RESULTS: ① The ATP contents of brain, myocardium and skeletal muscle were decreased significantly after acute exhaustive exercise. ②The activities of complex V, respiratory control rates (RCR) and ROS in mitochondria of brain, myocardium and skeletal muscle were decreased significantly after acute exhaustive exercise, respiration rate state 4(ST4) was increased significantly, at the same time, respiration rate state 3(ST3) had no significant difference. ③ The expression of PHB1 in mitochondria of skeletal muscle was decreased significantly after acute exhaustive exercise, while there was no significant change in PHB1 in myocardial tissue and mitochondria. ④ The correlation analysis showed that the ATP contents in the brain, myocardium and skeletal muscle were positively correlated with the activity of complex V and the expression of PHB1 after acute exhaustive exercise. CONCLUSIONS: After acute exhaustive exercise, the mitochondrial oxidative phosphorylation was reduced, the ROS production was increased, the expression of PHB1 was decreased, the ATP content and the activity of complex V were decreased in the brain and skeletal muscle of rats. Acute exhaustive exercise reduced the expression of PHB1 in mitochondria, decreased mitochondrial function, and reduced energy metabolism.