Skp2B attenuates p53 function by inhibiting prohibitin

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-022-00999-x.

Viral strategies for circumventing p53: the case of severe acute respiratory syndrome coronavirus

PURPOSE OF REVIEW

Virtually all viruses have evolved molecular instruments to circumvent cell mechanisms that may hamper their replication, dissemination, or persistence. Among these is p53, a key gatekeeper for cell division and survival that also regulates innate immune responses. This review summarizes the strategies used by different viruses and discusses the mechanisms deployed by SARS-CoV to target p53 activities.

RECENT FINDINGS

We propose a typology for the strategies used by different viruses to address p53 functions: hit and run (e.g. IAV, ZIKV), hide and seek (e.g. HIV1), kidnap and exploit (e.g. EBV, HSV1), dominate and suppress (e.g. HR HPV). We discuss the mechanisms by which SARS nsp3 protein targets p53 for degradation and we speculate on the significance for Covid-19 pathogenesis and risk of cancer.

SUMMARY

p53 may operate as an intracellular antiviral defense mechanism. To circumvent it, SARS viruses adopt a kidnap and exploit strategy also shared by several viruses with transforming potential. This raises the question of whether SARS infections may make cells permissive to oncogenic DNA damage.

Prohibitin ligands: a growing armamentarium to tackle cancers, osteoporosis, inflammatory, cardiac and neurological diseases

Over the last three decades, the scaffold proteins prohibitins-1 and -2 (PHB1/2) have emerged as key signaling proteins regulating a myriad of signaling pathways in health and diseases. Small molecules targeting PHBs display promising effects against cancers, osteoporosis, inflammatory, cardiac and neurodegenerative diseases. This review provides an updated overview of the various classes of PHB ligands, with an emphasis on their mechanism of action and therapeutic potential. We also describe how these ligands have been used to explore PHB signaling in different physiological and pathological settings.

Skp2 in the ubiquitin-proteasome system: A comprehensive review

The ubiquitin-proteasome system (UPS) is a complex process that regulates protein stability and activity by the sequential actions of E1, E2 and E3 enzymes to influence diverse aspects of eukaryotic cells. However, due to the diversity of proteins in cells, substrate selection is a highly critical part of the process. As a key player in UPS, E3 ubiquitin ligases recruit substrates for ubiquitination specifically. Among them, RING E3 ubiquitin ligases which are the most abundant E3 ubiquitin ligases contribute to diverse cellular processes. The multisubunit cullin-RING ligases (CRLs) are the largest family of RING E3 ubiquitin ligases with tremendous plasticity in substrate specificity and regulate a vast array of cellular functions. The F-box protein Skp2 is a component of CRL1 (the prototype of CRLs) which is expressed in many tissues and participates in multiple cellular functions such as cell proliferation, metabolism, and tumorigenesis by contributing to the ubiquitination and subsequent degradation of several specific tumor suppressors. Most importantly, Skp2 plays a pivotal role in a plethora of cancer-associated signaling pathways. It enhances cell growth, accelerates cell cycle progression, promotes migration and invasion, and inhibits cell apoptosis among others. Hence, targeting Skp2 may represent a novel and attractive strategy for the treatment of different human cancers overexpressing this oncogene. In this review article, we summarized the known roles of Skp2 both in health and disease states in relation to the UPS.

Recent insight into the role of FBXW7 as a tumor suppressor

FBXW7 (also known as Fbw7, Sel10, hCDC4, or hAgo) is a tumor suppressor and the most frequently mutated member of the F-box protein family in human cancers. FBXW7 functions as the substrate recognition component of an SCF-type E3 ubiquitin ligase. It specifically controls the proteasome-mediated degradation of many oncoproteins such as c-MYC, NOTCH, KLF5, cyclin E, c-JUN, and MCL1. In this review, we summarize the molecular and biological features of FBXW7 and its substrates as well as the impact of mutations of FBXW7 on cancer development. We also address the clinical potential of anticancer therapy targeting FBXW7.

Targeting SCF E3 Ligases for Cancer Therapies

SKP1-cullin-1-F-box-protein (SCF) E3 ubiquitin ligase complex is responsible for the degradation of proteins in a strictly regulated manner, through which it exerts pivotal roles in regulating various key cellular processes including cell cycle and division, apoptosis, and differentiation. The substrate specificity of the SCF complex largely depends on the distinct F-box proteins, which function in either tumor promotion or suppression or in a context-dependent manner. Among the 69 F-box proteins identified in human genome, FBW7, SKP2, and β-TRCP have been extensively investigated among various types of cancer in respective of their roles in cancer development, progression, and metastasis. Moreover, several specific inhibitors have been developed to target those E3 ligases, and their efficiency in tumors has been determined. In this review, we provide a summary of the roles of SCF E3 ligases in cancer development, as well as the potential application of miRNA or specific inhibitors for cancer therapy.

Targeted OMA1 therapies for cancer

The mitochondrial inner membrane proteins OMA1 and OPA1 belong to the BAX/BAK1-dependent apoptotic signaling pathway, which can be regulated by tumor protein p53 and the prohibitins PHB and PHB2 in the context of neoplastic disease. For the most part these proteins have been studied separate from each other. Here, I argue that the OMA1 mechanism of action represents the missing link between p53 and cytochrome c release. The mitochondrial fusion protein OPA1 is cleaved by OMA1 in a stress-dependent manner generating S-OPA1. Excessive S-OPA1 can facilitate outer membrane permeabilization upon BAX/BAK1 activation through its membrane shaping properties. p53 helps outer membrane permeabilization in a 2-step process. First, cytosolic p53 activates BAX/BAK1 at the mitochondrial surface. Then, in a second step, p53 binds to prohibitin thereby releasing the restraint on OMA1. This activates OMA1, which cleaves OPA1 and promotes cytochrome c release. Clearly, OMA1 and OPA1 are not root causes for cancer. Yet many cancer cells rely on this pathway for survival, which can explain why loss of p53 function promotes tumor growth and confers resistance to chemotherapies.

The IGF-p53 connection in cancer

Healthy tissue growth depends on a well-controlled and context-appropriate balance of cellular proliferation, cell cycle arrest, and programmed cell death (apoptosis). Disturbance of this balance by activation of oncogenes, inactivation/mutation of tumor suppressor genes, or inhibition of apoptosis can promote tumorigenesis. This mini-review will focus on evidence for the contribution of insulin-like growth factor (IGF) signaling and its regulation by the transcription factor, p53, to tumor development and progression.

Inhibition of Skp2 suppresses the proliferation and invasion of osteosarcoma cells

Osteosarcoma (OS) is a common bone tumor that mainly affects children and young adults. S-phase kinase‑associated protein 2 (Skp2) has been characterized to play a critical oncogenic role in a variety of human malignancies. However, the biological function of Skp2 in OS remains largely obscure. In the present study, we elucidated the role of Skp2 in cell growth, cell cycle, apoptosis and migration in OS cells. We found that depletion of Skp2 inhibited cell growth in both MG-63 and SW 1353 cells. Moreover, we observed that depletion of Skp2 triggered cell apoptosis in two OS cell lines. Furthermore, downregulation of Skp2 induced cell cycle arrest in the G0/G1 phase in OS cells. Notably, our wound healing assay results revealed that inhibition of Skp2 suppressed cell migration in OS cells. Invariably, our western blot results demonstrated that depletion of Skp2 in OS cells inhibited activation of pAkt and increased p27 expression in OS cells, suggesting that Skp2 exerted its oncogenic function partly through the regulation of Akt and p27. Our findings revealed that targeting Skp2 could be a promising therapeutic strategy for the treatment of OS.

Prohibitin promotes androgen receptor activation in ER-positive breast cancer

Prohibitin (PHB) is an evolutionarily conserved protein with multiple functions in both normal and cancer cells. Androgen receptor (AR) was reported to act as a different role in the ER-positive and ER-negative breast cancer. However, little is known about the role of PHB and whether PHB could regulate AR expression in the ER-positive breast cancer. Here, we determined the expression and clinical outcomes of PHB in breast cancer samples using 121 breast cancer tissues and published databases, and investigated the role of PHB in breast cancer cell growth, apoptosis and cell cycle arrest in the ER-positive breast cancer cells. We obtained the expression of PHB is significantly low in breast cancer samples, and low PHB expression positively correlated with poor prognosis of breast cancer. We detected that PHB could inhibit breast cancer cell proliferation, change cell cycle distribution and promote cell apoptosis in the ER-positive breast cancer cells. Moreover, we found PHB could significantly increase AR expression in both mRNA and protein levels in the ER-positive breast cancer cells. Additionally, a significant positive correlation between PHB and AR expression was identified in the 121 breast cancer tissues. PHB and AR expression are associated with prognosis in the ER-positive breast cancer patients. Our results indicate that PHB promotes AR activation in ER-positive breast cancer, making PHB and AR potential molecular targets for ER-positive breast cancer therapy.

Recent advances in SCF ubiquitin ligase complex: Clinical implications

F-box proteins, which are subunit recruiting modules of SCF (SKP1-Cullin 1-F-box protein) E3 ligase complexes, play critical roles in the development and progression of human malignancies through governing multiple cellular processes including cell proliferation, apoptosis, invasion and metastasis. Moreover, there are emerging studies that lead to the development of F-box proteins inhibitors with promising therapeutic potential. In this article, we describe how F-box proteins including but not restricted to well-established Fbw7, Skp2 and β-TRCP, are involved in tumorigenesis. However, in-depth investigation is required to further explore the mechanism and the physiological contribution of undetermined F-box proteins in carcinogenesis. Lastly, we suggest that targeting F-box proteins could possibly open new avenues for the treatment and prevention of human cancers.

Skp2 is over-expressed in breast cancer and promotes breast cancer cell proliferation

The F box protein Skp2 is oncogenic. Skp2 and Skp2B, an isoform of Skp2 are overexpressed in breast cancer. However, little is known regarding the mechanism by which Skp2B promotes the occurrence and development of breast cancer. Here, we determined the expression and clinical outcomes of Skp2 in breast cancer samples and cell lines using breast cancer database, and investigated the role of Skp2 and Skp2B in breast cancer cell growth, apoptosis and cell cycle arrest. We obtained Skp2 is significantly overexpressed in breast cancer samples and cell lines, and high Skp2 expression positively correlated with poor prognosis of breast cancer. Both Skp2 and Skp2B could promote breast cancer cell proliferation, inhibit cell apoptosis, change the cell cycle distribution and induce the increased S phase cells and therefore induce cell proliferation in breast cancer cells. Moreover, the 2 isoforms could both suppress PIG3 expression via independent pathways in the breast cancer cells. Skp2 suppressed p53 and inhibited PIG3-induced apoptosis, while Skp2B attenuated the function of PIG3 by inhibiting PHB. Our results indicate that Skp2 and Skp2B induce breast cancer cell development and progression, making Skp2 and Skp2B potential molecular targets for breast cancer therapy.

Arsenic Trioxide Inhibits Cell Growth and Invasion via Down- Regulation of Skp2 in Pancreatic Cancer Cells

Arsenic trioxide (ATO) has been found to exert anti-cancer activity in various human malignancies. However, the molecular mechanisms by which ATO inhibits tumorigenesis are not fully elucidated. In the current study, we explored the molecular basis of ATO-mediated tumor growth inhibition in pancreatic cancer cells. We used multiple approaches such as MTT assay, wound healing assay, Transwell invasion assay, annexin V-FITC, cell cycle analysis, RT-PCR and Western blotting to achieve our goal. We found that ATO treatment effectively caused cell growth inhibition, suppressed clonogenic potential and induced G2-M cell cycle arrest and apoptosis in pancreatic cancer cells. Moreover, we observed a significant down-regulation of Skp2 after treatment with ATO. Furthermore, we revealed that ATO regulated Skp2 downstream genes such as FOXO1 and p53. These findings demonstrate that inhibition of Skp2 could be a novel strategy for the treatment of pancreatic cancer by ATO.

p53 is required for cisplatin-induced processing of the mitochondrial fusion protein L-Opa1 that is mediated by the mitochondrial metallopeptidase Oma1 in gynecologic cancers

Mitochondria are highly dynamic organelles, and mitochondrial fission is a crucial step of apoptosis. Although Oma1 is believed to be responsible for long form Opa1 (L-Opa1) processing during mitochondrial fragmentation, whether and how Oma1 is involved in L-Opa1 processing and participates in the regulation of chemoresistance is unknown. Chemosensitive and chemoresistant ovarian (OVCA) and cervical (CECA) cancer cells were treated with cisplatin (CDDP). Mitochondrial dynamics and protein contents were assessed by immunofluorescence and Western blot, respectively. The requirements of Oma1 and p53 for CDDP-induced L-Opa1 processing, mitochondrial fragmentation, and apoptosis were examined by siRNA or cDNA. CDDP induces L-Opa1 processing and mitochondrial fragmentation in chemosensitive but not in chemoresistant cells. CDDP induced Oma1 40-kDa form increases in OV2008 cells, not in C13* cells. Oma1 knockdown inhibited L-Opa1 processing, mitochondrial fragmentation, and apoptosis. Silencing p53 expression attenuated the effects of CDDP in Oma1 (40 kDa) increase, L-Opa1 processing, mitochondrial fragmentation, and apoptosis in chemosensitive OVCA cells, whereas reconstitution of p53 in p53 mutant or null chemoresistant OVCA cells induced Oma1 (40 kDa) increase, L-Opa1 processing, mitochondrial fragmentation, and apoptosis irrespective of the presence of CDDP. Prohibitin 1 (Phb1) dissociates from Opa1-Phb1 complex and binds phosphorylated p53 (serine 15) in response to CDDP in chemosensitive but not chemoresistant CECA cells. These findings demonstrate that (a) p53 and Oma1 mediate L-Opa1 processing, (b) mitochondrial fragmentation is involved in CDDP-induced apoptosis in OVCA and CECA cells, and (c) dysregulated mitochondrial dynamics may in part be involved in the pathophysiology of CDDP resistance.

Prohibitin ligands in cell death and survival: mode of action and therapeutic potential

Prohibitins (PHBs) are scaffold proteins that modulate many signaling pathways controlling cell survival, metabolism, and inflammation. Several drugs that target PHBs have been identified and evaluated for various clinical applications. Preclinical and clinical studies indicate that these PHB ligands may be useful in oncology, cardiology, and neurology, as well as against obesity. This review covers the physiological role of PHBs in health and diseases and current developments concerning PHB ligands.

Signaling pathways of prohibitin and its role in diseases

Prohibitin (PHB), appearing to be a negative regulator of cell proliferation and to be a tumor suppressor, has been connected to diverse cellular functions including cell cycle control, senescence, apoptosis and the regulation of mitochondrial activities. It is a growth regulatory gene that has pleiotropic functions in the nucleus, mitochondria and cytoplasmic compartments. However, in different tissues/cells, the expression of PHB was different, such as that it was increased in most of the cancers, but its expression was reduced in kidney diseases. Signaling pathways might be very important in the pathogenesis of diseases. This review was performed to provide a relatively complete signaling pathways flowchart for PHB to the investigators who were interested in the roles of PHB in the pathogenesis of diseases. Here, we review the signal transduction pathways of PHB and its role in the pathogenesis of diseases.

p53, SKP2, and DKK3 as MYCN Target Genes and Their Potential Therapeutic Significance

Neuroblastoma is the most common extra-cranial solid tumor of childhood. Despite significant advances, it currently still remains one of the most difficult childhood cancers to cure, with less than 40% of patients with high-risk disease being long-term survivors. MYCN is a proto-oncogene implicated to be directly involved in neuroblastoma development. Amplification of MYCN is associated with rapid tumor progression and poor prognosis. Novel therapeutic strategies which can improve the survival rates whilst reducing the toxicity in these patients are therefore required. Here we discuss genes regulated by MYCN in neuroblastoma, with particular reference to p53, SKP2, and DKK3 and strategies that may be employed to target them.

Flotillin-1 promotes tumor necrosis factor-α receptor signaling and activation of NF-κB in esophageal squamous cell carcinoma cells

BACKGROUND & AIMS

The flotillin family of proteins, including flotillin-1 (FLOT1 or Reggie-2), are lipid raft proteins that initiate receptor kinase signaling and are up-regulated in several tumor types. We investigated the role of FLOT1 signaling and activation of the transcription factor nuclear factor (NF)-κB in esophageal squamous cell carcinoma (ESCC) cells.

METHODS

We used immunoblot and immunochemical analyses to determine levels of the lipid raft-associated protein FLOT1 in ESCC cell lines and 432 ESSC samples from patients; primary normal esophageal epithelial cells and matched adjacent nontumor tissues were used as controls. We determined the ability of FLOT1 to activate NF-κB using kinase, electrophoretic mobility shift, and luciferase reporter assays. We measured the effects of FLOT1 overexpression and knockdown with short hairpin RNAs in ESCC cell lines using colony formation, anchorage-independent growth, chicken chorioallantoic membrane, transwell matrix penetration, and Annexin V-binding assays. We analyzed growth of ESCC xenograft tumors in nude mice.

RESULTS

Levels of FLOT1 were increased in ESCC cell lines and samples from patients, compared with controls; protein levels correlated with disease stage and survival time. Overexpression of FLOT1 in Kyse30 and Kyse510 ESCC cell lines increased proliferation, anchorage-independent growth, and invasive activity and protected them from apoptosis. FLOT1-transduced ESCC cells formed larger tumors in nude mice than control cells (transduced with only the vector). FLOT1 facilitated recruitment of the tumor necrosis factor-α receptor to lipid rafts; promoted K63-linked polyubiquitination of the signaling intermediaries tumor necrosis factor receptor associated factor 2, receptor interacting protein, and NEMO; and sustained the activation of NF-κB. Levels of FLOT1 correlated with activation of NF-κB in ESCC samples from patients.

CONCLUSIONS

The lipid raft protein FLOT1 is up-regulated in ESCC cell lines and samples from patients and promotes ESCC cell proliferation and tumor growth in mice. FLOT1 activates tumor necrosis factor-α receptor signaling and sustains activation of NF-κB in ESCC cells.

Prohibitin attenuates colitis-associated tumorigenesis in mice by modulating p53 and STAT3 apoptotic responses

Although inflammatory bowel disease is associated with higher risk of colorectal cancer, the precise pathogenic mechanisms underlying this association are not completely understood. Prohibitin 1 (PHB), a protein implicated in the regulation of proliferation, apoptosis, and transcription, is decreased in intestinal inflammation. In this study, we have established a key function for PHB in mediating colitis-associated cancer. Wild-type and transgenic (Tg) mice specifically overexpressing PHB in intestinal epithelial cells were subjected to a classical two-stage protocol of colitis-associated carcinogenesis. In addition, wild-type and p53 null human cell models were used to assess PHB interaction with STAT3 and p53. Wild-type mice exhibited decreased mucosal PHB protein expression during colitis-associated carcinogenesis. Tg mice exhibited decreased susceptibility in a manner associated with increased apoptosis, p53, Bax, and Bad expression plus decreased Bcl-xL and Bcl-2 expression. PHB overexpression in wild-type but not p53 null human cells increased expression of Bax, Bad, and caspase-3 cleavage. In wild-type p53 cells, PHB overexpression decreased basal and interleukin-6-induced STAT3 activation and expression of the STAT3 responsive genes Bcl-xL and Bcl-2. PHB coimmunoprecipitated with phospho-STAT3 in addition to p53 in cultured cell lysates and colon mucosa. This is the first study to show interaction between PHB and STAT3 in vivo. In summary, our findings suggest that PHB protects against colitis-associated cancer by modulating p53- and STAT3-mediated apoptosis. Modulation of PHB expression in intestinal epithelial cells may offer a potential therapeutic approach to prevent colitis-associated carcinogenesis.

Skp2 is a promising therapeutic target in breast cancer

Breast cancer is the most common type of cancer among American women, and remains the second leading cause of cancer-related death for female in the United States. It has been known that several signaling pathways and various factors play critical roles in the development and progression of breast cancer, such as estrogen receptor, Notch, PTEN, human epidermal growth factor receptor 2, PI3K/Akt, BRCA1, and BRCA2. Emerging evidence has shown that the F-box protein S-phase kinase associated protein 2 (Skp2) also plays an important role in the pathogenesis of breast cancer. Therefore, in this brief review, we summarize the novel functions of Skp2 in the pathogenesis of breast cancer. Moreover, we provide further evidence regarding the state of our knowledge toward the development of novel Skp2 inhibitors especially natural "chemopreventive agents" as targeted approach for the prevention and/or treatment of breast cancer.

Skp2B overexpression alters a prohibitin-p53 axis and the transcription of PAPP-A, the protease of insulin-like growth factor binding protein 4

Background

We previously reported that the degradation of prohibitin by the SCF^Skp2B ubiquitin ligase results in a defect in the activity of p53. We also reported that MMTV-Skp2B transgenic mice develop mammary gland tumors that are characterized by an increased proteolytic cleavage of the insulin-like growth factor binding protein 4 (IGFBP-4), an inhibitor of IGF signaling. However, whether a link exists between a defect in p53 activity and proteolysis of IGFBP-4 was not established.

Methods and Results

We analyzed the levels of pregnancy-associated plasma protein A (PAPP-A), the protease of IGFBP-4, in MMTV-Skp2B transgenic mice and found that PAPP-A levels are elevated. Further, we found a p53 binding site in intron 1 of the PAPP-A gene and that both wild type and mutant p53 bind to this site. However, binding of wild type p53 results in the transcriptional repression of PAPP-A, while binding of mutant p53 results in the transcriptional activation of PAPP-A. Since MMTV-Skp2B mice express wild type p53 and yet show elevated levels of PAPP-A, at first, these observations appeared contradictory. However, further analysis revealed that the defect in p53 activity in Skp2B overexpressing cells does not only abolish the activity of wild type of p53 but actually mimics that of mutant p53. Our results suggest that in absence of prohibitin, the half-life of p53 is increased and like mutant p53, the conformation of p53 is denatured.

Conclusions

These observations revealed a novel function of prohibitin as a chaperone of p53. Further, they suggest that binding of denatured p53 in intron 1 causes an enhancer effect and increases the transcription of PAPP-A. Therefore, these findings indicate that the defect in p53 function and the increased proteolysis of IGFBP-4, we had observed, represent two components of the same pathway, which contributes to the oncogenic function of Skp2B.

Lipid rafts: signaling and sorting platforms of cells and their roles in cancer

Lipid rafts are defined as microdomains within the lipid bilayer of cellular membranes that assemble subsets of transmembrane or glycosylphosphatidylinisotol-anchored proteins and lipids (cholesterol and sphingolipids) and experimentally resist extraction in cold detergent (detergent-resistant membrane). These highly dynamic raft domains are essential in signaling processes and also form sorting platforms for targeted protein traffic. Lipid rafts are involved in protein endocytosis that occurs via caveolae or flotillin-dependent pathways. Non-constitutive protein components of rafts fluctuate dramatically in cancer with impacts on cell proliferation, signaling, protein trafficking, adhesion and apoptosis. This article focuses on the identification of candidate cancer-associated biomarkers in carcinoma cells using state-of-the-art proteomics.

The role and therapeutic potential of prohibitin in disease

Prohibitin 1 (PHB1), a pleiotropic protein in the cell, has been implicated in the regulation of proliferation, apoptosis, transcription, mitochondrial protein folding, and as a cell-surface receptor. This diverse array of functions of PHB1 is attributed to the cell type studied and its subcellular localization. This review discusses recent data that indicate a diverse role of PHB1 in disease pathogenesis and suggest that targeting PHB1 may be a potential therapeutic option for treatment of diseases including cancer, inflammatory bowel disease, insulin resistance/type 2 diabetes, and obesity. These diseases are associated with increased oxidative stress and mitochondrial dysfunction and therefore, the role of PHB1 in both responses will also be discussed.