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Zhang M, Lin Y, Chen R, Yu H, Li Y, Chen M, Dou C, Yin P, Zhang L, Tang P. Ghost messages: cell death signals spread. Cell Commun Signal 2023; 21:6. [PMID: 36624476 PMCID: PMC9830882 DOI: 10.1186/s12964-022-01004-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 11/24/2022] [Indexed: 01/11/2023] Open
Abstract
Cell death is a mystery in various forms. Whichever type of cell death, this is always accompanied by active or passive molecules release. The recent years marked the renaissance of the study of these molecules showing they can signal to and communicate with recipient cells and regulate physio- or pathological events. This review summarizes the defined forms of messages cells could spread while dying, the effects of these signals on the target tissue/cells, and how these types of communications regulate physio- or pathological processes. By doing so, this review hopes to identify major unresolved questions in the field, formulate new hypothesis worthy of further investigation, and when possible, provide references for the search of novel diagnostic/therapeutics agents. Video abstract.
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Affiliation(s)
- Mingming Zhang
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Yuan Lin
- grid.412463.60000 0004 1762 6325Department of Orthopedics, The Second Affiliated Hospital of Harbin Medical University, Harbin, 150001 Heilongjiang People’s Republic of China
| | - Ruijing Chen
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Haikuan Yu
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Yi Li
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Ming Chen
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Ce Dou
- grid.410570.70000 0004 1760 6682Department of Orthopedics, Southwest Hospital, Army Medical University, Chongqing, 400038 People’s Republic of China
| | - Pengbin Yin
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Licheng Zhang
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
| | - Peifu Tang
- grid.414252.40000 0004 1761 8894Department of Orthopedics, Chinese PLA General Hospital, Beijing, 100853 People’s Republic of China ,National Clinical Research Center for Orthopedics, Sports Medicine and Rehabilitation, Beijing, 100853 People’s Republic of China
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TTYH3 Modulates Bladder Cancer Proliferation and Metastasis via FGFR1/H-Ras/A-Raf/MEK/ERK Pathway. Int J Mol Sci 2022; 23:ijms231810496. [PMID: 36142409 PMCID: PMC9501546 DOI: 10.3390/ijms231810496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 08/31/2022] [Accepted: 09/07/2022] [Indexed: 12/09/2022] Open
Abstract
Tweety family member 3 (TTYH3) is a calcium-activated chloride channel with a non-pore-forming structure that controls cell volume and signal transduction. We investigated the role of TTYH3 as a cancer-promoting factor in bladder cancer. The mRNA expression of TTYH3 in bladder cancer patients was investigated using various bioinformatics databases. The results demonstrated that the increasingly greater expression of TTYH3 increasingly worsened the prognosis of patients with bladder cancer. TTYH3 knockdown bladder cancer cell lines were constructed by their various cancer properties measured. TTYH3 knockdown significantly reduced cell proliferation and sphere formation. Cell migration and invasion were also significantly reduced in knockdown bladder cancer cells, compared to normal bladder cancer cells. The knockdown of TTYH3 led to the downregulation of H-Ras/A-Raf/MEK/ERK signaling by inhibiting fibroblast growth factor receptor 1 (FGFR1) phosphorylation. This signaling pathway also attenuated the expression of c-Jun and c-Fos. The findings implicate TTYH3 as a potential factor regulating the properties of bladder cancer and as a therapeutic target.
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Muñoz-Maldonado C, Zimmer Y, Medová M. A Comparative Analysis of Individual RAS Mutations in Cancer Biology. Front Oncol 2019; 9:1088. [PMID: 31681616 PMCID: PMC6813200 DOI: 10.3389/fonc.2019.01088] [Citation(s) in RCA: 136] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Accepted: 10/02/2019] [Indexed: 01/15/2023] Open
Abstract
In human cells, three closely related RAS genes, termed HRAS, KRAS, and NRAS, encode four highly homologous proteins. RAS proteins are small GTPases involved in a broad spectrum of key molecular and cellular activities, including proliferation and survival among others. Gain-of-function missense mutations, mostly located at codons 12, 13, and 61, constitutively activate RAS proteins and can be detected in various types of human cancers. KRAS is the most frequently mutated, followed by NRAS and HRAS. However, each isoform exhibits distinctive mutation frequency at each codon, supporting the hypothesis that different RAS mutants may lead to distinct biologic manifestations. This review is focused on the differences in signaling and phenotype, as well as on transcriptomics, proteomics, and metabolomics profiles related to individual RAS-mutated variants. Additionally, association of these mutants with particular targeted outcomes and rare mutations at additional RAS codons are discussed.
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Affiliation(s)
- Carmen Muñoz-Maldonado
- Department of Radiation Oncology, Inselspital, Bern University Hospital, Bern, Switzerland.,Radiation Oncology, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Yitzhak Zimmer
- Department of Radiation Oncology, Inselspital, Bern University Hospital, Bern, Switzerland.,Radiation Oncology, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Michaela Medová
- Department of Radiation Oncology, Inselspital, Bern University Hospital, Bern, Switzerland.,Radiation Oncology, Department for BioMedical Research, University of Bern, Bern, Switzerland
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Adeniji EA, Olotu FA, Soliman MES. Exploring the Lapse in Druggability: Sequence Analysis, Structural Dynamics and Binding Site Characterization of K-RasG12C Variant, a Feasible Oncotherapeutics Target. Anticancer Agents Med Chem 2019; 18:1540-1550. [PMID: 30019652 DOI: 10.2174/1871520618666180718110231] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/28/2018] [Accepted: 07/04/2018] [Indexed: 12/24/2022]
Abstract
BACKGROUND The difficulty in druggability of K-Ras variant has presented a challenge in the treatment of cancer diseases associated with its dysfunctionality. Despite the identification of different binding sites, limited information exists in the literature about their characteristics. Therefore, identification, crossvalidation and characterization of its druggable sites would aid the design of chemical compounds that will arrest its dysfunctionality related oncogenesis. OBJECTIVE This study entails the identification, cross-validation and characterization of K-Ras G12C variant's binding sites for potential druggability, coupled with the elucidation of alterations in 3D conformations and dynamics. METHOD Molecular dynamics simulation was carried out on the inactive, the active and the hyperactive K-RasG12Cvariant using the amber software package. The SiteMap software was employed in identifying and characterizing the druggable binding sites while the validation of the binding sites was carried out with the SiteHound and MetaPocket servers. RESULTS Four druggable binding sites were identified, validated and characterized based on physicochemical attributes such as size, volume, degree of enclosure or exposure, degree of contact, hydrophobic/hydrophilic character, hydrophobic/hydrophilic balance and hydrogen-bonding features. Conformational studies also revealed that the K-Ras variant exhibited notable structural instability, increased flexibility and a strongly anticorrelated movement compared to the inactive and active wildtype forms. CONCLUSION The attributes of the characterized druggable sites will be useful in designing site-specific K-Ras inhibitors for the treatment of K-Ras variant associated cancer diseases.
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Affiliation(s)
- Emmanuel A Adeniji
- Molecular Bio-Computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
| | - Fisayo A Olotu
- Molecular Bio-Computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
| | - Mahmoud E S Soliman
- Molecular Bio-Computation and Drug Design Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4001, South Africa
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Kumar N, Shrungeswara AH, Mallik SB, Biswas S, Mathew J, Nandakumar K, Mathew J, Lobo R. Pinocembrin-Enriched Fractions of Elytranthe parasitica (L.) Danser Modulates Apoptotic and MAPK Cellular Signaling in HepG2 Cells. Anticancer Agents Med Chem 2019; 18:1563-1572. [DOI: 10.2174/1871520618666180911112127] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 08/20/2018] [Accepted: 09/03/2018] [Indexed: 12/22/2022]
Abstract
Background:
Hepatocellular carcinoma (HCC) is the fifth leading cause of cáncer mortality. Elytranthe
parasitica (L.) Danser (EP), a hemiparasitic plant (Loranthaceae) has potent anti-cancer properties.
Objective:
In the study, we investigated the effect of EP fractions on the expression of apoptosis and mitogenactivated
protein kinase (MAPK) markers deregulated in HCC. Bioactivity fractionation was performed to isolate the
phytochemical(s) exerting anti-tumor activity in HepG2 cells.
Method:
Anti-proliferative, clonogenic and anti-metastatic effects of EP fractions were examined in hepatocellular
carcinoma cell line, HepG2 by Sulphorhodamine B, colony formation and scratch wound assays respectively in
hepatocellular cell line, HepG2. The effects of EP fractions on key markers of apoptosis and MAPK signaling pathways
were explored.
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Key findings: EP bioactive fractions showed significant anti-tumor potential, reduced clonogenicity and considerably
inhibited cell migration in HepG2 cells in vitro. The fractions augmented annexin V binding and induced apoptosis
by causing cell cycle arrest at G2/M and S phase checkpoints. The fractions increased expression levels of p53, bad,
cleaved PARP (Poly ADP ribose polymerase) and cleaved Caspase-3. Expression levels of phosphorylated ERK1/2
(Extracellular signal-regulated kinase) were downregulated. Pinocembrin-7-O-ß-D-glucoside and chrysin were isolated
and characterized for the first time from Elytranthe parasitica (L.) Danser.
Conclusion:
Our findings reveal that EP fractions induced cell cycle arrest and triggered apoptosis in HepG2 cells by
upregulating apoptosis and deactivating MAPK pathway. It signifies that pinocembrin glycoside and chrysin are
bioactive phytochemicals contributing to the potent anti-hepatocarcinoma effects on HepG2 cells. Hence, bioactive
EP fractions could be used as a therapeutic agent for effective HCC therapy.
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Affiliation(s)
- Nimmy Kumar
- Department of Pharmacognosy, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
| | - Akhila H. Shrungeswara
- Department of Pharmacy Practice, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
| | - Sanchari B. Mallik
- Department of Pharmacology, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
| | - Subhankar Biswas
- Department of Pharmacology, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
| | - Jesil Mathew
- Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
| | - Krishnadas Nandakumar
- Department of Pharmacology, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
| | - Jessy Mathew
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Richard Lobo
- Department of Pharmacognosy, Manipal College of Pharmaceutical Sciences, Karnataka 576104, India
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Shukla A, Dahiya S, Onteru SK, Singh D. Differentially expressed miRNA-210 during follicular-luteal transition regulates pre-ovulatory granulosa cell function targeting HRas and EFNA3. J Cell Biochem 2018; 119:7934-7943. [PMID: 29131373 DOI: 10.1002/jcb.26508] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 10/09/2017] [Indexed: 01/19/2023]
Abstract
Ovarian folliculogenesis, ovulation, and luteinization are an important prerequisite for fertility performance in mammals. Spatial and temporal key factors and proteins for their regulation are well known. Recent advancement in the field of molecular biology led to the discovery of another class of gene regulators, microRNA (miRNA). Previous studies on profiling of miRNA in buffalo ovaries revealed that miRNA-210 (miR-210) is differently expressed in follicular-luteal transition. Therefore, the present study was planned to ascertain the role of miR-210 in buffalo granulosa cells. Cultured granulosa cells were transfected with miR-210 mimic. Effect of overexpression of miR-210 was analyzed on granulosa cell marker genes (CYP19A1 and PCNA) which were significantly downregulated (P < 0.05). Further, target genes of miR-210 were screened using Target Scan software v7.1 and a list of 37 genes with cumulative weight context score (CWCS) > 0.5 was sorted followed by their functional annotation and network analyses using PANTHER and STRING software. Bioinformatics analyses identified HRas gene as a potential hub gene of miR-210 targeted genes. HRas has been shown to be involved in diverse biological pathways regulating ovarian functions. An expression analysis of HRas was further validated both in vitro and in vivo. EFNA3 (EFHRIN-A3), another identified target of miR-210 known to be involved in angiogenesis, was also downregulated in miR-210 transfected granulosa cells. In conclusion, the present study demonstrated that miR-210 can regulate granulosa cell function at preovulatory stage through HRas and EFNA3. Further studies are needed to find the mechanism how miR-210 regulates the granulosa cells function through these targets.
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Affiliation(s)
- Astha Shukla
- Molecular Endocrinology, Functional Genomics and Systems Biology Laboratory, Animal Biochemistry Division, National Dairy Research Institute, Karnal, Haryana, India
| | - Sunita Dahiya
- Molecular Endocrinology, Functional Genomics and Systems Biology Laboratory, Animal Biochemistry Division, National Dairy Research Institute, Karnal, Haryana, India
| | - Suneel K Onteru
- Molecular Endocrinology, Functional Genomics and Systems Biology Laboratory, Animal Biochemistry Division, National Dairy Research Institute, Karnal, Haryana, India
| | - Dheer Singh
- Molecular Endocrinology, Functional Genomics and Systems Biology Laboratory, Animal Biochemistry Division, National Dairy Research Institute, Karnal, Haryana, India
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Nakhaei-Rad S, Haghighi F, Nouri P, Rezaei Adariani S, Lissy J, Kazemein Jasemi NS, Dvorsky R, Ahmadian MR. Structural fingerprints, interactions, and signaling networks of RAS family proteins beyond RAS isoforms. Crit Rev Biochem Mol Biol 2018; 53:130-156. [PMID: 29457927 DOI: 10.1080/10409238.2018.1431605] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Saeideh Nakhaei-Rad
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Fereshteh Haghighi
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Parivash Nouri
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Soheila Rezaei Adariani
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Jana Lissy
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Neda S Kazemein Jasemi
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Radovan Dvorsky
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
| | - Mohammad Reza Ahmadian
- a Institute of Biochemistry and Molecular Biology II, Medical Faculty , Heinrich-Heine University , Düsseldorf , Germany
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Warszawski S, Netzer R, Tawfik DS, Fleishman SJ. A "fuzzy"-logic language for encoding multiple physical traits in biomolecules. J Mol Biol 2014; 426:4125-4138. [PMID: 25311857 PMCID: PMC4270444 DOI: 10.1016/j.jmb.2014.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/21/2014] [Accepted: 10/02/2014] [Indexed: 12/16/2022]
Abstract
To carry out their activities, biological macromolecules balance different physical traits, such as stability, interaction affinity, and selectivity. How such often opposing traits are encoded in a macromolecular system is critical to our understanding of evolutionary processes and ability to design new molecules with desired functions. We present a framework for constraining design simulations to balance different physical characteristics. Each trait is represented by the equilibrium fractional occupancy of the desired state relative to its alternatives, ranging from none to full occupancy, and the different traits are combined using Boolean operators to effect a "fuzzy"-logic language for encoding any combination of traits. In another paper, we presented a new combinatorial backbone design algorithm AbDesign where the fuzzy-logic framework was used to optimize protein backbones and sequences for both stability and binding affinity in antibody-design simulation. We now extend this framework and find that fuzzy-logic design simulations reproduce sequence and structure design principles seen in nature to underlie exquisite specificity on the one hand and multispecificity on the other hand. The fuzzy-logic language is broadly applicable and could help define the space of tolerated and beneficial mutations in natural biomolecular systems and design artificial molecules that encode complex characteristics.
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Affiliation(s)
- Shira Warszawski
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ravit Netzer
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Dan S Tawfik
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sarel J Fleishman
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
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Park YH, Kim SU, Lee BK, Kim HS, Song IS, Shin HJ, Han YH, Chang KT, Kim JM, Lee DS, Kim YH, Choi CM, Kim BY, Yu DY. Prx I suppresses K-ras-driven lung tumorigenesis by opposing redox-sensitive ERK/cyclin D1 pathway. Antioxid Redox Signal 2013; 19. [PMID: 23186333 PMCID: PMC3704122 DOI: 10.1089/ars.2011.4421] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
AIMS Coupled responses of mutated K-ras and oxidative stress are often an important etiological factor in non-small-cell lung cancer (NSCLC). However, relatively few studies have examined the control mechanism of oxidative stress in oncogenic K-ras-driven NSCLC progression. Here, we studied whether the redox signaling pathway governed by peroxiredoxin I (Prx I) is involved in K-ras(G12D)-mediated lung adenocarcinogenesis. RESULTS Using human-lung adenocarcinoma tissues and lung-specific K-ras(G12D)-transgenic mice, we found that Prx I was significantly up-regulated in the tumor regions via activation of nuclear erythroid 2-related factor 2 (Nrf2) transcription. Interestingly, the increased reactive oxygen species (ROS) by null mutation of Prx I greatly promoted K-ras(G12D)-driven lung tumorigenesis in number and size, which appeared to require the activation of the ROS-dependent extracellular signal-regulated kinase (ERK)/cyclin D1 pathway. INNOVATION Taken together, these results suggest that Prx I functions as an Nrf2-dependently inducible tumor suppressant in K-ras-driven lung adenocarcinogenesis by opposing ROS/ERK/cyclin D1 pathway activation. CONCLUSION These findings provide a better understanding of oxidative stress-mediated lung tumorigenesis.
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Affiliation(s)
- Young-Ho Park
- Disease Model Research Laboratory, Aging Research Center , Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
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Paquin MC, Cagnol S, Carrier JC, Leblanc C, Rivard N. ERK-associated changes in E2F4 phosphorylation, localization and transcriptional activity during mitogenic stimulation in human intestinal epithelial crypt cells. BMC Cell Biol 2013; 14:33. [PMID: 23919615 PMCID: PMC3750237 DOI: 10.1186/1471-2121-14-33] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 08/02/2013] [Indexed: 01/12/2023] Open
Abstract
Background The transcription factor E2F4 controls proliferation of normal and cancerous intestinal epithelial cells. E2F4 localization in normal human intestinal epithelial cells (HIEC) is cell cycle-dependent, being cytoplasmic in quiescent differentiated cells but nuclear in proliferative cells. However, the intracellular signaling mechanisms regulating such E2F4 localization remain unknown. Results Treatment of quiescent HIEC with serum induced ERK1/2 activation, E2F4 phosphorylation, E2F4 nuclear translocation and G1/S phase transition while inhibition of MEK/ERK signaling by U0126 prevented these events. Stimulation of HIEC with epidermal growth factor (EGF) also led to the activation of ERK1/2 but, in contrast to serum or lysophosphatidic acid (LPA), EGF failed to induce E2F4 phosphorylation, E2F4 nuclear translocation and G1/S phase transition. Furthermore, Akt and GSK3β phosphorylation levels were markedly enhanced in serum- or LPA-stimulated HIEC but not by EGF. Importantly, E2F4 phosphorylation, E2F4 nuclear translocation and G1/S phase transition were all observed in response to EGF when GSK3 activity was concomitantly inhibited by SB216763. Finally, E2F4 was found to be overexpressed, phosphorylated and nuclear localized in epithelial cells from human colorectal adenomas exhibiting mutations in APC and KRAS or BRAF genes, known to deregulate GSK3/β-catenin and MEK/ERK signaling, respectively. Conclusions The present results indicate that MEK/ERK activation and GSK3 inhibition are both required for E2F4 phosphorylation as well as its nuclear translocation and S phase entry in HIEC. This finding suggests that dysregulated E2F4 nuclear localization may be an instigating event leading to hyperproliferation and hence, of tumor initiation and promotion in the colon and rectum.
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Affiliation(s)
- Marie-Christine Paquin
- Département d'Anatomie et Biologie Cellulaire, Cancer Research Pavillon, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, 3201, Jean-Mignault, Sherbrooke, J1E4K8, QC, Canada
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Flinder LI, Wierød L, Rosseland CM, Huitfeldt HS, Skarpen E. FAK regulates Cdk2 in EGF-stimulated primary cultures of hepatocytes. J Cell Physiol 2013; 228:1304-13. [PMID: 23168795 DOI: 10.1002/jcp.24287] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 11/06/2012] [Indexed: 12/19/2022]
Abstract
In this study, we report a novel role of FAK as a regulator of Cdk2 in anchorage-dependent primary cultured hepatocytes. In response to EGF, we found that S-phase entry was reduced upon FAK inhibition. This correlated with decreased protein expression and nuclear accumulation of the G1/S-phase regulator Cdk2. Further, nuclear accumulation of the Cdk2 partner cyclinE, was reduced, but not its protein level. Also, protein levels of Cdk2 were inversely linked with increased expression of the Cdk2 inhibitor p27, known to be degraded in a Cdk2-dependent manner. Also, cyclinD1 was regulated by FAK, but to a lesser extent than Cdk2. To assess the mechanism in which FAK mediates Cdk2-regulation, FAK mutants were used: FAKY397F, mutated at its integrin-regulated site, and two others mutated at docking sites for Grb2-ERK-activation (FAKY925F) and for p130Cas-Rac1-activation (FAKY861F). All three sites were central for EGF-induced ERK-activity and Cdk2 expression. In addition, FAK was important for HGF-mediated proliferation, suggesting a general mechanism for anchorage-dependent growth. Moreover, growth factor-induced cell spreading, but not survival, required FAK. Hence, integrins and growth factors cooperate in anchorage-dependent signaling events leading to proliferation and motility. In conclusion, our data suggest that FAK acts as a central coordinator of integrin and growth factor-mediated S-phase entry by its ability to regulate Cdk2.
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Affiliation(s)
- Liv Ingrid Flinder
- Laboratory for Toxicopathology, Institute of Pathology, Oslo University Hospital, University of Oslo, Oslo, Norway
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Shi JH, Liu SZ, Wierød L, Scholz H, Anmarkrud JA, Huitfeldt HS, Zhang SJ, Line PD. RAF-targeted therapy for hepatocellular carcinoma in the regenerating liver. J Surg Oncol 2012; 107:393-401. [PMID: 22927239 DOI: 10.1002/jso.23224] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 06/25/2012] [Indexed: 01/19/2023]
Abstract
BACKGROUND Post-operative liver regeneration may contribute to tumor recurrence. There is a theoretical need for an adjuvant therapy that can suppress tumor growth without adversely affecting post-operative liver regeneration. OBJECTIVE To evaluate the effect of RAF inhibitor Sorafenib on cell viability and proliferation of hepatoma cells and hepatocytes in vitro and in an in vivo rat model. METHODS Cell viability, DNA synthesis, and RAF/MAPK kinase activity in the primary hepatocyte and hepatoma cell lines were investigated after Sorafenib exposure. Sequence analysis of the B-RAF gene in hepatic cells was determined. Tumor markers were compared within the rats after 70% hepatectomy with or without daily oral gavages of Sorafenib. Liver regeneration was assessed by liver function tests and proliferation markers. RESULTS Primary hepatocytes showed higher cell viability, proliferation rate, and stronger RAF/MAPK kinase activity compared with hepatoma cell lines. The in vivo tumor volumes, size, and metastases were significantly decreased (P < 0.05) whereas no significant change in liver regeneration related to Sorafenib exposure was found (P > 0.05). B-RAF V600E mutation was not detected neither in the hepatic cells nor untransformed hepatocytes. CONCLUSIONS The RAF targeted inhibitor can reduce tumor growth without retarding liver regeneration in this experiment.
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Affiliation(s)
- Ji-Hua Shi
- Department of Transplantation, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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Figueiredo ML, Stein TJ, Jochem A, Sandgren EP. Mutant Hras(G12V) and Kras(G12D) have overlapping, but non-identical effects on hepatocyte growth and transformation frequency in transgenic mice. Liver Int 2012; 32:582-91. [PMID: 22221894 PMCID: PMC4319543 DOI: 10.1111/j.1478-3231.2011.02732.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 11/28/2011] [Indexed: 12/24/2022]
Abstract
BACKGROUND Mouse hepatocarcinogenesis is associated with mutations in Hras, but infrequently in Kras. The effect on carcinogenesis of developmental age at the time of ras mutation remains unknown. AIM We sought to compare quantitatively the effects of expressing mutant H- or Kras genes in fetal vs. adult mouse liver. METHODS We established an inducible system of gene expression in mouse liver to define disease pathogenesis associated with activation of oncogene expression. RESULTS Diffuse expression of either oncogene in fetal or adult hepatocytes caused hepatomegaly. For mutant Hras(G12V), this phenotype was almost fully reversible and accompanied by apoptosis, indicating that maintenance of hepatomegaly requires continuous Hras(G12V) expression. We also examined the effect of ras expression on growth of transplanted hepatocytes in an in vivo system that allows us to quantify hepatocyte growth effects in both permissive and restrictive hepatic growth environments. Mutant Kras(G12D) had no effect on hepatocyte growth in this system. In contrast, Hras(G12V) induced increased hepatocyte focus growth in quiescent liver, the hallmark of a cell autonomous growth stimulus. Hras(G12V) also increased the fraction of donor hepatocyte foci that displayed extreme growth, a characteristic of preneoplastic lesions. CONCLUSIONS The primary effect of diffuse, whole-liver expression of either mutant ras gene in fetal or adult mouse liver is diffuse and progressive hepatic growth. Hras(G12V) mutation influences hepatocarcinogenesis by conferring cell autonomous growth potential upon foci of expressing cells and by increasing the risk of neoplastic progression. Kras(G12D) does not share these latter carcinogenic effects in mouse liver.
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Affiliation(s)
- Marxa L. Figueiredo
- Department of Pathobiological Sciences; School of Veterinary Medicine; University of Wisconsin-Madison; Madison; WI; USA
| | - Timothy J. Stein
- Department of Pathobiological Sciences; School of Veterinary Medicine; University of Wisconsin-Madison; Madison; WI; USA
| | - Adam Jochem
- Department of Pathobiological Sciences; School of Veterinary Medicine; University of Wisconsin-Madison; Madison; WI; USA
| | - Eric P. Sandgren
- Department of Pathobiological Sciences; School of Veterinary Medicine; University of Wisconsin-Madison; Madison; WI; USA
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Fuentes-Calvo I, Blázquez-Medela AM, Eleno N, Santos E, López-Novoa JM, Martínez-Salgado C. H-Ras isoform modulates extracellular matrix synthesis, proliferation, and migration in fibroblasts. Am J Physiol Cell Physiol 2011; 302:C686-97. [PMID: 22094331 DOI: 10.1152/ajpcell.00103.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ras GTPases are ubiquitous plasma membrane transducers of extracellular stimuli. In addition to their role as oncogenes, Ras GTPases are key regulators of cell function. Each of the Ras isoforms exhibits specific modulatory activity on different cellular pathways. This has prompted researchers to determine the pathophysiological roles of each isoform. There is a proven relationship between the signaling pathways of transforming growth factor-β1 (TGF-β1) and Ras GTPases. To assess the individual role of H-Ras oncogene in basal and TGF-β1-mediated extracellular matrix (ECM) synthesis, proliferation, and migration in fibroblasts, we analyzed these processes in embryonic fibroblasts obtained from H-Ras knockout mice (H-ras(-/-)). We found that H-ras(-/-) fibroblasts exhibited a higher basal phosphatidylinositol-3-kinase (PI3K)/Akt activation than wild-type (WT) fibroblasts, whereas MEK/ERK 1/2 activation was similar in both types of cells. Fibronectin and collagen synthesis were higher in H-ras(-/-) fibroblasts and proliferation was lower in H-ras(-/-) than in WT fibroblasts. Moreover, H-Ras appeared indispensable to maintain normal fibroblast motility, which was highly restricted in H-ras(-/-) cells. These results suggest that H-Ras (through downregulation of PI3K/Akt activation) could modulate fibroblast activity by reducing ECM synthesis and upregulating both proliferation and migration. TGF-β1 strongly increased ERK and Akt activation in WT but not in H-ras(-/-) fibroblasts, suggesting that H-Ras is necessary to increase ERK 1/2 activation and to maintain PI3K downregulation in TGF-β1-stimulated fibroblasts. TGF-β1 stimulated ECM synthesis and proliferation, although ECM synthesis was higher and proliferation lower in H-ras(-/-) than in WT fibroblasts. Hence, H-Ras activation seems to play a key role in the regulation of these effects.
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Affiliation(s)
- Isabel Fuentes-Calvo
- Unidad de Fisiopatología Renal y Cardiovascular, Instituto “Reina Sofía” de Investigación Nefrológica, Departamento de Fisiología y Farmacología, Universidad de Salamanca, Salamanca, Spain
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15
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Galectin-3 mediates cross-talk between K-Ras and Let-7c tumor suppressor microRNA. PLoS One 2011; 6:e27490. [PMID: 22102901 PMCID: PMC3216962 DOI: 10.1371/journal.pone.0027490] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 10/18/2011] [Indexed: 01/02/2023] Open
Abstract
Background Galectin-3 (Gal-3) and active (GTP-bound) K-Ras contribute to the malignant phenotype of many human tumors by increasing the rate of cell proliferation, survival, and migration. These Gal-3-mediated effects result from a selective binding to K-Ras.GTP, causing increased nanoclustering in the cell membrane and leading to robust Ras signaling. Regulation of the interactions between Gal-3 and active K-Ras is not fully understood. Methods and Findings To gain a better understanding of what regulates the critical interactions between these two proteins, we examined the role of Gal-3 in the regulation of K-Ras by using Gal-3-knockout mouse embryonic-fibroblasts (Gal-3-/- MEFs) and/or Gal-3/Gal-1 double-knockout MEFs. We found that knockout of Gal-3 induced strong downregulation (∼60%) of K-Ras and K-Ras.GTP. The downregulation was somewhat more marked in the double-knockout MEFs, in which we also detected robust inhibition(∼50%) of ERK and Akt activation. These additional effects are probably attributable to inhibition of the weak interactions of K-Ras.GTP with Gal-1. Re-expression of Gal-3 reversed the phenotype of the Gal-3-/- MEFs and dramatically reduced the disappearance of K-Ras in the presence of cycloheximide to the levels seen in wild-type MEFs. Furthermore, phosphorylation of Gal-3 by casein kinase-1 (CK-1) induced translocation of Gal-3 from the nucleus to the cytoplasm and the plasma membrane, leading to K-Ras stabilization accompanied by downregulation of the tumor suppressor miRNA let-7c, known to negatively control K-Ras transcription. Conclusions Our results suggest a novel cross-talk between Gal-3-mediated downregulation of let 7c microRNA (which in turn negatively regulates K-Ras transcription) and elucidates the association among Gal-3 let-7c and K-Ras transcription/translation, cellular compartmentalization and activity.
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16
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Castellano E, Santos E. Functional specificity of ras isoforms: so similar but so different. Genes Cancer 2011; 2:216-31. [PMID: 21779495 DOI: 10.1177/1947601911408081] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
H-ras, N-ras, and K-ras are canonical ras gene family members frequently activated by point mutation in human cancers and coding for 4 different, highly related protein isoforms (H-Ras, N-Ras, K-Ras4A, and K-Ras4B). Their expression is nearly ubiquitous and broadly conserved across eukaryotic species, although there are quantitative and qualitative differences of expression depending on the tissue and/or developmental stage under consideration. Extensive functional studies have determined during the last quarter century that these Ras gene products are critical components of signaling pathways that control eukaryotic cell proliferation, survival, and differentiation. However, because of their homology and frequent coexpression in various cellular contexts, it remained unclear whether the different Ras proteins play specific or overlapping functional roles in physiological and pathological processes. Initially, their high degree of sequence homology and the observation that all Ras isoforms share common sets of downstream effectors and upstream activators suggested that they were mostly redundant functionally. In contrast, the notion of functional specificity for each of the different Ras isoforms is supported at present by an increasing body of experimental observations, including 1) the fact that different ras isoforms are preferentially mutated in specific types of tumors or developmental disorders; 2) the different transforming potential of transfected ras genes in different cell contexts; 3) the distinct sensitivities exhibited by the various Ras family members for modulation by different GAPs or GEFs; 4) the demonstration that different Ras isoforms follow distinct intracellular processing pathways and localize to different membrane microdomains or subcellular compartments; 5) the different phenotypes displayed by genetically modified animal strains for each of the 3 ras loci; and 6) the specific transcriptional networks controlled by each isoform in different cellular settings.
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Affiliation(s)
- Esther Castellano
- Signal Transduction Laboratory, Cancer Research UK London Research Institute, London, UK
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Lu CY, Li CC, Lii CK, Yao HT, Liu KL, Tsai CW, Chen HW. Andrographolide-induced pi class of glutathione S-transferase gene expression via PI3K/Akt pathway in rat primary hepatocytes. Food Chem Toxicol 2010; 49:281-9. [PMID: 21056613 DOI: 10.1016/j.fct.2010.10.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 10/08/2010] [Accepted: 10/31/2010] [Indexed: 01/18/2023]
Abstract
Andrographis paniculata is an herb widely used in China, Korea, and India for its anti-hepatotoxic, anti-viral, and anti-inflammatory effects. Andrographolide is the major bioactive diterpene lactone in A. paniculata. The pi class of glutathione S-transferase (GSTP) is one of the phase II biotransformation enzymes. Our previous study indicated that andrographolide upregulates the expression of GSTP. The aim of this study was to investigate the mechanism by which andrographolide induces GSTP gene expression in rat primary hepatocytes. In hepatocytes treated with 40 μM andrographolide, immunoblots showed maximal Akt phosphorylation at 0.5 h and maximal c-jun phosphorylation at 3 h. However, pretreatment with PI3K inhibitors, wortmannin and LY294002, or siPI3K inhibited the andrographolide-induced phosphorylation of c-jun and GSTP protein expression. EMSA showed that pretreatment with wortmannin, LY294002, or siPI3K attenuated the AP-1-DNA-binding activity caused by andrographolide. Results of immunoprecipitation indicated that nuclear c-fos/c-jun heterodimer increases with andrographolide treatment. Addition of antibodies against c-jun and c-fos decreased nuclear protein bound to the AP-1 consensus DNA sequence. In summary, andrographolide induces GSTP gene expression in rat primary hepatocytes through activation of the PI3K/Akt, phosphorylation of c-jun, nuclear accumulation of AP-1, and subsequent binding to the response element in the gene promoter region.
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Affiliation(s)
- Chia-Yang Lu
- Department of Nutrition, Chung Shan Medical University, Taichung, Taiwan
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18
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Wu CH, Shih YW, Chang CH, Ou TT, Huang CC, Hsu JD, Wang CJ. EP4 upregulation of Ras signaling and feedback regulation of Ras in human colon tissues and cancer cells. Arch Toxicol 2010; 84:731-40. [PMID: 20571779 DOI: 10.1007/s00204-010-0562-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Accepted: 05/07/2010] [Indexed: 01/24/2023]
Abstract
Previous studies indicate that COX-2 and prostaglandin E(2) (PGE(2)) receptor subtypes are involved in intestinal carcinogenesis and activation of downstream pathways. In this report, we try to understand the association of PGE(2) receptor and K-ras cellular mechanism during the development of colorectal cancer. We collected 21 colorectal cancer patients and compared the protein expression of tumor tissues and normal mucosa tissues by using immunoblot. Furthermore, we transferred empty vector and pcDNA-K-ras into Ras-HT29 colon cancer cells. Result showed that phosphorylation of Akt and EP(1)/EP(4) were over-expressed in the colorectal tumor tissue. K-ras induces HT29 cells proliferation through the expressions of COX-2, EP1/EP4, pAkt, GSK3beta and increases Tcf transcriptional factor activation. Additionally, Ras protein was suppressed when treated with EP(4) inhibitor in Ras-HT29 cell. In cell cycle assay, K-ras mutation causing cell cycle S phase was prolonged with an increase in the G2/M phase ratio. In conclusion, we suggested that Ras overexpression leads to cell proliferation through activating Ras/PI3K/GSK3beta/EP(4) PGE(2) receptor signals and caused a feedback regulation of Ras by EP4 in colorectal tumor progression.
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Affiliation(s)
- Cheng-Hsun Wu
- Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung 402, Taiwan, Republic of China
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Genome-wide gene expression analysis identifies K-ras as a regulator of alcohol intake. Brain Res 2010; 1339:1-10. [PMID: 20388501 DOI: 10.1016/j.brainres.2010.03.063] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 03/17/2010] [Indexed: 12/30/2022]
Abstract
Adaptations in the anterior cingulate cortex (ACC) have been implicated in alcohol and drug addiction. To identify genes that may contribute to excessive drinking, here we performed microarray analyses in laser microdissected rat ACC after a single or repeated administration of an intoxicating dose of alcohol (3 g/kg). Expression of the small G protein K-ras was differentially regulated following both single and repeated alcohol administration. We also observed that voluntary alcohol intake in K-ras heterozygous null mice (K-ras(+/-)) did not increase after withdrawal from repeated cycles of intermittent ethanol vapor exposure, unlike in their wild-type littermates. To identify K-ras regulated pathways, we then profiled gene expression in the ACC of K-ras(+/-), heterozygous null mice for the K-ras negative regulator Nf1 (Nf1(+/-)) and wild-type mice following repeated administration of an intoxicating dose of alcohol. Pathway analysis showed that alcohol differentially affected various pathways in a K-ras dependent manner - some of which previously shown to be regulated by alcohol - including the insulin/PI3K pathway, the NF-kappaB, the phosphodiesterases (PDEs) pathway, the Jak/Stat and the adipokine signaling pathways. Altogether, the data implicate K-ras-regulated pathways in the regulation of excessive alcohol drinking after a history of dependence.
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Godoy P, Hengstler JG, Ilkavets I, Meyer C, Bachmann A, Müller A, Tuschl G, Mueller SO, Dooley S. Extracellular matrix modulates sensitivity of hepatocytes to fibroblastoid dedifferentiation and transforming growth factor beta-induced apoptosis. Hepatology 2009; 49:2031-43. [PMID: 19274752 DOI: 10.1002/hep.22880] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Hepatocytes in culture are a valuable tool to investigate mechanisms involved in the response of the liver to cytokines. However, it is well established that hepatocytes cultured on monolayers of dried stiff collagen dedifferentiate, losing specialized liver functions. In this study, we show that hepatocyte dedifferentiation is a reversible consequence of a specific signaling network constellation triggered by the extracellular matrix. A dried stiff collagen activates focal adhesion kinase (FAK) via Src, leading to activation of the Akt and extracellular signal-regulated kinase (ERK) 1/2 pathways. Akt causes resistance to transforming growth factor beta (TGF-beta)-induced apoptosis by antagonizing p38, whereas ERK1/2 signaling opens the route to epithelial-mesenchymal transition (EMT). Apoptosis resistance is reversible by inhibiting Akt or Src, and EMT can be abrogated by blocking the ERK1/2 pathway. In contrast to stiff collagen, a softer collagen gel does not activate FAK, keeping the hepatocytes in a state where they remain sensitive to TGF-beta-induced apoptosis and do not undergo EMT. In this culture system, inhibition of p38 as well as overexpression of constitutively active Akt causes apoptosis resistance, whereas constitutively active Ras induces EMT. Finally, we show that matrix-induced EMT is reversible by replating cells from dried stiff to soft gel collagen. Our results demonstrate that hepatocyte dedifferentiation in vitro is an active process driven by FAK-mediated Akt and ERK1/2 signaling. This leads to similar functional and morphological alterations as observed for regenerating hepatocytes in vivo and is reversible when Akt and/or ERK1/2 signaling pathways are antagonized. CONCLUSION Hepatocytes can exist in a differentiated and a dedifferentiated state that are reversible and can be switched by manipulating the responsible key factors of the signaling network.
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Affiliation(s)
- Patricio Godoy
- Molecular Alcohol Research in Gastroenterology, Department of Medicine II, Faculty of Medicine at Mannheim, University of Heidelberg, Germany
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Aivatiadou E, Ripolone M, Brunetti F, Berruti G. cAMP-Epac2-mediated activation of Rap1 in developing male germ cells: RA-RhoGAP as a possible direct down-stream effector. Mol Reprod Dev 2009; 76:407-16. [PMID: 18937323 DOI: 10.1002/mrd.20963] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Rap1 is a small GTPase that functions as a positional signal and organizer of cell architecture. Recently Rap1 is emerged to play a critical role during sperm differentiation since its inactivation in haploid cells leads to a premature release of spermatids from the supporting Sertoli cell resulting in male infertility. How Rap1 is activated in spermatogenic cells has not yet been determined. Our objective was to investigate on a possible cAMP-mediated activation of Rap1 employing a cAMP analogue selective to Epac, the Rap1 activator directly responsive to cAMP, for stimulating cultured testis germ cells. Here we provide biochemical, cellular and functional evidence that the Epac variant known as Epac2 is expressed as both a transcript and a protein and that it is able to promote Rap1 activation in the cultured cells. A time course immunofluorescence analysis carried out on stimulated cells revealed the translocation of endogenous Epac2, which is cytosolic, towards the site where Rap1 is located, i.e., the Golgi complex, thus documenting the effective Rap1-Epac2 protein interaction 'in vivo' leading to Rap1-GTP loading. A combination of biochemical and molecular techniques supported the immunofluorescence data. The search for the presence of a putative Rap1 downstream effector, described in differentiating somatic cells as a target of cAMP-Epac-activated Rap1, revealed the presence in spermatogenic cells of RA-RhoGAP, a Rap1-activated Rho GTPase-activating protein. Taken together, our results, obtained with endogenously expressed proteins, are consistent with a cAMP/Epac2/Rap1-mediated signaling that could exert its action, among others, through RA-RhoGAP to promote the progression of spermatogenesis.
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Affiliation(s)
- Evanthia Aivatiadou
- Laboratory of Cellular and Molecular Biology of Reproduction, Department of Biology, University of Milan, Italy
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