1
|
Michalak DJ, Unger B, Lorimer E, Grishaev A, Williams CL, Heinrich F, Lösche M. Structural and biophysical properties of farnesylated KRas interacting with the chaperone SmgGDS-558. Biophys J 2022; 121:3684-3697. [PMID: 35614853 PMCID: PMC9617131 DOI: 10.1016/j.bpj.2022.05.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 05/02/2022] [Accepted: 05/19/2022] [Indexed: 11/26/2022] Open
Abstract
KRas is a small GTPase and membrane-bound signaling protein. Newly synthesized KRas is post-translationally modified with a membrane-anchoring prenyl group. KRas chaperones are therapeutic targets in cancer due to their participation in trafficking oncogenic KRas to membranes. SmgGDS splice variants are chaperones for small GTPases with basic residues in their hypervariable domain (HVR), including KRas. SmgGDS-607 escorts pre-prenylated small GTPases, while SmgGDS-558 escorts prenylated small GTPases. We provide a structural description of farnesylated and fully processed KRas (KRas-FMe) in complex with SmgGDS-558 and define biophysical properties of this interaction. Surface plasmon resonance measurements on biomimetic model membranes quantified the thermodynamics of the interaction of SmgGDS with KRas, and small-angle x-ray scattering was used to characterize complexes of SmgGDS-558 and KRas-FMe structurally. Structural models were refined using Monte Carlo and molecular dynamics simulations. Our results indicate that SmgGDS-558 interacts with the HVR and the farnesylated C-terminus of KRas-FMe, but not its G-domain. Therefore, SmgGDS-558 interacts differently with prenylated KRas than prenylated RhoA, whose G-domain was found in close contact with SmgGDS-558 in a recent crystal structure. Using immunoprecipitation assays, we show that SmgGDS-558 binds the GTP-bound, GDP-bound, and nucleotide-free forms of farnesylated and fully processed KRas in cells, consistent with SmgGDS-558 not engaging the G-domain of KRas. We found that the dissociation constant, Kd, for KRas-FMe binding to SmgGDS-558 is comparable with that for the KRas complex with PDEδ, a well-characterized KRas chaperone that also does not interact with the KRas G-domain. These results suggest that KRas interacts in similar ways with the two chaperones SmgGDS-558 and PDEδ. Therapeutic targeting of the SmgGDS-558/KRas complex might prove as useful as targeting the PDEδ/KRas complex in KRas-driven cancers.
Collapse
Affiliation(s)
- Dennis J Michalak
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Bethany Unger
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Ellen Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Alexander Grishaev
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland; Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania; Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland.
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania; Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland
| |
Collapse
|
2
|
Brandt AC, Koehn OJ, Williams CL. SmgGDS: An Emerging Master Regulator of Prenylation and Trafficking by Small GTPases in the Ras and Rho Families. Front Mol Biosci 2021; 8:685135. [PMID: 34222337 PMCID: PMC8242357 DOI: 10.3389/fmolb.2021.685135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 05/27/2021] [Indexed: 11/17/2022] Open
Abstract
Newly synthesized small GTPases in the Ras and Rho families are prenylated by cytosolic prenyltransferases and then escorted by chaperones to membranes, the nucleus, and other sites where the GTPases participate in a variety of signaling cascades. Understanding how prenylation and trafficking are regulated will help define new therapeutic strategies for cancer and other disorders involving abnormal signaling by these small GTPases. A growing body of evidence indicates that splice variants of SmgGDS (gene name RAP1GDS1) are major regulators of the prenylation, post-prenylation processing, and trafficking of Ras and Rho family members. SmgGDS-607 binds pre-prenylated small GTPases, while SmgGDS-558 binds prenylated small GTPases. This review discusses the history of SmgGDS research and explains our current understanding of how SmgGDS splice variants regulate the prenylation and trafficking of small GTPases. We discuss recent evidence that mutant forms of RabL3 and Rab22a control the release of small GTPases from SmgGDS, and review the inhibitory actions of DiRas1, which competitively blocks the binding of other small GTPases to SmgGDS. We conclude with a discussion of current strategies for therapeutic targeting of SmgGDS in cancer involving splice-switching oligonucleotides and peptide inhibitors.
Collapse
Affiliation(s)
- Anthony C Brandt
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Olivia J Koehn
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| |
Collapse
|
3
|
Sato T, Mukai S, Ikeda H, Mishiro-Sato E, Akao K, Kobayashi T, Hino O, Shimono W, Shibagaki Y, Hattori S, Sekido Y. Silencing of SmgGDS, a Novel mTORC1 Inducer That Binds to RHEBs, Inhibits Malignant Mesothelioma Cell Proliferation. Mol Cancer Res 2021; 19:921-931. [PMID: 33574130 DOI: 10.1158/1541-7786.mcr-20-0637] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 12/15/2020] [Accepted: 02/04/2021] [Indexed: 11/16/2022]
Abstract
Malignant mesothelioma (MM) is an aggressive tumor that typically develops after a long latency following asbestos exposure. Although mechanistic target of rapamycin complex 1 (mTORC1) activation enhances MM cell growth, the mTORC1 inhibitor everolimus has shown limited efficacy in clinical trials of MM patients. We explored the mechanism underlying mTORC1 activation in MM cells and its effects on cell proliferation and progression. Analysis of the expression profiles of 87 MMs from The Cancer Genome Atlas revealed that 40 samples (46%) displayed altered expression of RPTOR (mTORC1 component) and genes immediately upstream that activate mTORC1. Among them, we focused on RHEB and RHEBL1, which encode direct activators of mTORC1. Exogenous RHEBL1 expression enhanced MM cell growth, indicating that RHEB-mTORC1 signaling acts as a pro-oncogenic cascade. We investigated molecules that directly activate RHEBs, identifying SmgGDS as a novel RHEB-binding protein. SmgGDS knockdown reduced mTORC1 activation and inhibited the proliferation of MM cells with mTORC1 activation. Interestingly, SmgGDS displayed high binding affinity with inactive GDP-bound RHEBL1, and its knockdown reduced cytosolic RHEBL1 without affecting its activation. These findings suggest that SmgGDS retains GDP-bound RHEBs in the cytosol, whereas GTP-bound RHEBs are localized on intracellular membranes to promote mTORC1 activation. We revealed a novel role for SmgGDS in the RHEB-mTORC1 pathway and its potential as a therapeutic target in MM with aberrant mTORC1 activation. IMPLICATIONS: Our data showing that SmgGDS regulates RHEB localization to activate mTORC1 indicate that SmgGDS can be used as a new therapeutic target for MM exhibiting mTORC1 activation.
Collapse
Affiliation(s)
- Tatsuhiro Sato
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Satomi Mukai
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Haruna Ikeda
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Emi Mishiro-Sato
- Division of Pathophysiology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Ken Akao
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan.,Department of Respiratory Medicine, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Toshiyuki Kobayashi
- Department of Molecular Pathogenesis, Graduate School of Medicine, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Okio Hino
- Department of Molecular Pathogenesis, Graduate School of Medicine, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Wataru Shimono
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Yoshio Shibagaki
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Seisuke Hattori
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Yoshitaka Sekido
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan. .,Division of Molecular and Cellular Oncology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
| |
Collapse
|
4
|
Asiri A, Aloyouni E, Umair M, Alyafee Y, Al Tuwaijri A, Alhamoudi KM, Almuzzaini B, Al Baz A, Alwadaani D, Nashabat M, Alfadhel M. Mutated RAP1GDS1 causes a new syndrome of dysmorphic feature, intellectual disability & speech delay. Ann Clin Transl Neurol 2020; 7:956-964. [PMID: 32431071 PMCID: PMC7318102 DOI: 10.1002/acn3.51059] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 04/01/2020] [Accepted: 04/27/2020] [Indexed: 01/12/2023] Open
Abstract
Background RAP1GDS1 (RAP1, GTP‐GDP dissociation stimulator 1), also known as SmgGDS, is a guanine nucleotide exchange factor (GEF) that regulates small GTPases, including, RHOA, RAC1, and KRAS. RAP1GDS1 was shown to be highly expressed in different tissue types including the brain. However, mutations in the RAP1GDS1 gene associated with human diseases have not previously been reported. Methods We report on four affected individuals, presenting intellectual disability, global developmental delay (GDD), and hypotonia. The probands’ DNA was subjected to whole‐genome sequencing, revealing a homozygous splice acceptor site mutation in the RAP1GDS1 gene (1444‐1G > A). Sanger sequencing was performed to confirm the segregation of the variant in two Saudi families. The possible aberrant splicing in the patients’ RNA was investigated using RT‐PCR and changes in mRNA expression of the patients were confirmed using qRT‐PCR. Results The identified splice variant was found to segregate within the two families. RT‐PCR showed that the mutation affected RAP1GDS1 gene splicing, resulting in the production of aberrant transcripts in the affected individuals. Quantitative gene expression analysis demonstrated that the RAP1GDS1 mRNA expression in all the probands was significantly decreased compared to that of the control, and Sanger sequencing of the probands’ cDNA revealed skipping of exon 13, further strengthening the pathogenicity of this variant. Conclusion We are the first to report the mutation of the RAP1GDS1 gene as a potential cause of GDD and hypotonia. However, further investigations into the molecular mechanisms involved are required to confirm the role of RAP1GDS1 gene in causing GDD and hypotonia.
Collapse
Affiliation(s)
- Abdulaziz Asiri
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Essra Aloyouni
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Muhammad Umair
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Yusra Alyafee
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Abeer Al Tuwaijri
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Kheloud M Alhamoudi
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Bader Almuzzaini
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Abeer Al Baz
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Deemah Alwadaani
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
| | - Marwan Nashabat
- Division of Genetics, Department of Pediatrics, King Abdullah Specialized Children's Hospital, King Saud Bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Majid Alfadhel
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, King AbdulAziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia.,Division of Genetics, Department of Pediatrics, King Abdullah Specialized Children's Hospital, King Saud Bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| |
Collapse
|
5
|
Splice switching an oncogenic ratio of SmgGDS isoforms as a strategy to diminish malignancy. Proc Natl Acad Sci U S A 2020; 117:3627-3636. [PMID: 32019878 DOI: 10.1073/pnas.1914153117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The chaperone protein SmgGDS promotes cell-cycle progression and tumorigenesis in human breast and nonsmall cell lung cancer. Splice variants of SmgGDS, named SmgGDS-607 and SmgGDS-558, facilitate the activation of oncogenic members of the Ras and Rho families of small GTPases through membrane trafficking via regulation of the prenylation pathway. SmgGDS-607 interacts with newly synthesized preprenylated small GTPases, while SmgGDS-558 interacts with prenylated small GTPases. We determined that cancer cells have a high ratio of SmgGDS-607:SmgGDS-558 (607:558 ratio), and this elevated ratio is associated with reduced survival of breast cancer patients. These discoveries suggest that targeting SmgGDS splicing to lower the 607:558 ratio may be an effective strategy to inhibit the malignant phenotype generated by small GTPases. Here we report the development of a splice-switching oligonucleotide, named SSO Ex5, that lowers the 607:558 ratio by altering exon 5 inclusion in SmgGDS pre-mRNA (messenger RNA). Our results indicate that SSO Ex5 suppresses the prenylation of multiple small GTPases in the Ras, Rho, and Rab families and inhibits ERK activity, resulting in endoplasmic reticulum (ER) stress, the unfolded protein response, and ultimately apoptotic cell death in breast and lung cancer cell lines. Furthermore, intraperitoneal (i.p.) delivery of SSO Ex5 in MMTV-PyMT mice redirects SmgGDS splicing in the mammary gland and slows tumorigenesis in this aggressive model of breast cancer. Taken together, our results suggest that the high 607:558 ratio is required for optimal small GTPase prenylation, and validate this innovative approach of targeting SmgGDS splicing to diminish malignancy in breast and lung cancer.
Collapse
|
6
|
Structural Insights into the Regulation Mechanism of Small GTPases by GEFs. Molecules 2019; 24:molecules24183308. [PMID: 31514408 PMCID: PMC6767298 DOI: 10.3390/molecules24183308] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 12/12/2022] Open
Abstract
Small GTPases are key regulators of cellular events, and their dysfunction causes many types of cancer. They serve as molecular switches by cycling between inactive guanosine diphosphate (GDP)-bound and active guanosine triphosphate (GTP)-bound states. GTPases are deactivated by GTPase-activating proteins (GAPs) and are activated by guanine-nucleotide exchange factors (GEFs). The intrinsic GTP hydrolysis activity of small GTPases is generally low and is accelerated by GAPs. GEFs promote GDP dissociation from small GTPases to allow for GTP binding, which results in a conformational change of two highly flexible segments, called switch I and switch II, that enables binding of the gamma phosphate and allows small GTPases to interact with downstream effectors. For several decades, crystal structures of many GEFs and GAPs have been reported and have shown tremendous structural diversity. In this review, we focus on the latest structural studies of GEFs. Detailed pictures of the variety of GEF mechanisms at atomic resolution can provide insights into new approaches for drug discovery.
Collapse
|
7
|
GEF mechanism revealed by the structure of SmgGDS-558 and farnesylated RhoA complex and its implication for a chaperone mechanism. Proc Natl Acad Sci U S A 2018; 115:9563-9568. [PMID: 30190425 DOI: 10.1073/pnas.1804740115] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
SmgGDS has dual functions in cells and regulates small GTPases as both a guanine nucleotide exchange factor (GEF) for the Rho family and a molecular chaperone for small GTPases possessing a C-terminal polybasic region followed by four C-terminal residues called the CaaX motif, which is posttranslationally prenylated at its cysteine residue. Our recent structural work revealed that SmgGDS folds into tandem copies of armadillo-repeat motifs (ARMs) that are not present in other GEFs. However, the precise mechanism of GEF activity and recognition mechanism for the prenylated CaaX motif remain unknown because SmgGDS does not have a typical GEF catalytic domain and lacks a pocket to accommodate a prenyl group. Here, we aimed to determine the crystal structure of the SmgGDS/farnesylated RhoA complex. We found that SmgGDS induces a significant conformational change in the switch I and II regions that opens up the nucleotide-binding site, with the prenyl group fitting into the cryptic pocket in the N-terminal ARMs. Taken together, our findings could advance the understanding of the role of SmgGDS and enable drug design strategies for targeting SmgGDS and small GTPases.
Collapse
|
8
|
Overexpression of the VRK1 kinase, which is associated with breast cancer, induces a mesenchymal to epithelial transition in mammary epithelial cells. PLoS One 2018; 13:e0203397. [PMID: 30180179 PMCID: PMC6122820 DOI: 10.1371/journal.pone.0203397] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 08/20/2018] [Indexed: 01/23/2023] Open
Abstract
Vaccinia-related kinase 1 (VRK1) is a pro-proliferative nuclear kinase. Mice engrafted with VRK1-depleted MDA-MB-231 breast cancer cells have been shown to develop fewer distal metastases than controls, suggesting VRK1 might play a role in cell migration, invasion, and/or colonization. In work described herein, we investigated the impact of VRK1 overexpression on human mammary epithelial cells. In 2D culture, VRK1 overexpression diminishes cell migration and invasion and impairs the migration-associated processes of cell spreading and cytoskeletal rearrangement. VRK1-overexpressing cells show reduced accumulation of the mesenchymal marker vimentin and increased accumulation of the epithelial markers E-cadherin and claudin-1. VRK1 overexpression also leads to reduced levels of the transcriptional repressors snail, slug, and twist1. Cumulatively, these data indicate that VRK1 overexpression augments the epithelial properties of both MCF10a and MDA-MB-231 cells. We further studied the impact of VRK1 on the epithelial properties of MCF10a cells in 3D matrigel culture, in which cells proliferate and form epithelial sheets that mature into hollow spherical acini. VRK1 overexpression significantly accelerates the initial stages of cell proliferation, leading to larger acini that nevertheless differentiate and mature. Our analysis of human tumor tissue microarrays (TMAs) revealed that VRK1 protein levels are higher in lymph node metastases than in patient-matched mammary tumors. Using public databases, we determined that VRK1 is among the top 10% of overexpressed transcripts in multiple subtypes of invasive breast cancer, and that high levels of VRK1 expression are correlated with decreased relapse-free survival. In sum, overexpression of VRK1, by regulating the transcription repressors snail, slug, and twist1, can promote a mesenchymal-to-epithelial transition (MET) in cell culture. VRK1-mediated MET might facilitate the colonization of distal sites by metastatic breast cancer cells, providing some insight into the frequent association of VRK1 overexpression with breast malignancies and the correlation between VRK1 overexpression and poor clinical outcome.
Collapse
|
9
|
Gonyo P, Bergom C, Brandt AC, Tsaih SW, Sun Y, Bigley TM, Lorimer EL, Terhune SS, Rui H, Flister MJ, Long RM, Williams CL. SmgGDS is a transient nucleolar protein that protects cells from nucleolar stress and promotes the cell cycle by regulating DREAM complex gene expression. Oncogene 2017; 36:6873-6883. [PMID: 28806394 PMCID: PMC5730474 DOI: 10.1038/onc.2017.280] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 06/07/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022]
Abstract
The chaperone protein and guanine nucleotide exchange factor SmgGDS (RAP1GDS1) is a key promoter of cancer cell proliferation and tumorigenesis. SmgGDS undergoes nucleocytoplasmic shuttling, suggesting that it has both cytoplasmic and nuclear functions that promote cancer. Previous studies indicate that SmgGDS binds cytoplasmic small GTPases and promotes their trafficking to the plasma membrane. In contrast, little is known about the functions of SmgGDS in the nucleus, or how these nuclear functions might benefit cancer cells. Here we show unique nuclear localization and regulation of gene transcription pathways by SmgGDS. Strikingly, SmgGDS depletion significantly reduces expression of over 600 gene products that are targets of the DREAM complex, which is a transcription factor complex that regulates expression of proteins controlling the cell cycle. The cell cycle regulators E2F1, MYC, MYBL2 (B-Myb) and FOXM1 are among the DREAM targets that are diminished by SmgGDS depletion. E2F1 is well known to promote G1 cell cycle progression, and the loss of E2F1 in SmgGDS-depleted cells provides an explanation for previous reports that SmgGDS depletion characteristically causes a G1 cell cycle arrest. We show that SmgGDS localizes in nucleoli, and that RNAi-mediated depletion of SmgGDS in cancer cells disrupts nucleolar morphology, signifying nucleolar stress. We show that nucleolar SmgGDS interacts with the RNA polymerase I transcription factor upstream binding factor (UBF). The RNAi-mediated depletion of UBF diminishes nucleolar localization of SmgGDS and promotes proteasome-mediated degradation of SmgGDS, indicating that nucleolar sequestration of SmgGDS by UBF stabilizes SmgGDS protein. The ability of SmgGDS to interact with UBF and localize in the nucleolus is diminished by expressing DiRas1 or DiRas2, which are small GTPases that bind SmgGDS and act as tumor suppressors. Taken together, our results support a novel nuclear role for SmgGDS in protecting malignant cells from nucleolar stress, thus promoting cell cycle progression and tumorigenesis.
Collapse
Affiliation(s)
- P Gonyo
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - C Bergom
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - A C Brandt
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - S-W Tsaih
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Y Sun
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - T M Bigley
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Pediatrics, Washington University in St Louis, St Louis, MO, USA
| | - E L Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - S S Terhune
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - H Rui
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - M J Flister
- Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Human and Molecular Genetics Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - R M Long
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA.,Medical College of Wisconsin Central Wisconsin Campus, Wausau, WI, USA
| | - C L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA
| |
Collapse
|
10
|
Shimizu H, Toma-Fukai S, Saijo S, Shimizu N, Kontani K, Katada T, Shimizu T. Structure-based analysis of the guanine nucleotide exchange factor SmgGDS reveals armadillo-repeat motifs and key regions for activity and GTPase binding. J Biol Chem 2017; 292:13441-13448. [PMID: 28630045 PMCID: PMC5555202 DOI: 10.1074/jbc.m117.792556] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 06/14/2017] [Indexed: 01/15/2023] Open
Abstract
Small GTPases are molecular switches that have critical biological roles and are controlled by GTPase-activating proteins and guanine nucleotide exchange factors (GEFs). The smg GDP dissociation stimulator (SmgGDS) protein functions as a GEF for the RhoA and RhoC small GTPases. SmgGDS has various regulatory roles, including small GTPase trafficking and localization and as a molecular chaperone, and interacts with many small GTPases possessing polybasic regions. Two SmgGDS splice variants, SmgGDS-558 and SmgGDS-607, differ in GEF activity and binding affinity for RhoA depending on the lipidation state, but the reasons for these differences are unclear. Here we determined the crystal structure of SmgGDS-558, revealing a fold containing tandem copies of armadillo repeats not present in other GEFs. We also observed that SmgGDS harbors distinct positively and negatively charged regions, both of which play critical roles in binding to RhoA and GEF activity. This is the first report demonstrating a relationship between the molecular function and atomic structure of SmgGDS. Our findings indicate that the two SmgGDS isoforms differ in GTPase binding and GEF activity, depending on the lipidation state, thus providing useful information about the cellular functions of SmgGDS in cells.
Collapse
Affiliation(s)
- Hikaru Shimizu
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Sachiko Toma-Fukai
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shinya Saijo
- the Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan, and
| | - Nobutaka Shimizu
- the Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan, and
| | - Kenji Kontani
- the Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose-shi, Tokyo 204-8588, Japan
| | - Toshiaki Katada
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Toshiyuki Shimizu
- From the Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan,
| |
Collapse
|
11
|
Bergom C, Hauser AD, Rymaszewski A, Gonyo P, Prokop JW, Jennings BC, Lawton AJ, Frei A, Lorimer EL, Aguilera-Barrantes I, Mackinnon AC, Noon K, Fierke CA, Williams CL. The Tumor-suppressive Small GTPase DiRas1 Binds the Noncanonical Guanine Nucleotide Exchange Factor SmgGDS and Antagonizes SmgGDS Interactions with Oncogenic Small GTPases. J Biol Chem 2016; 291:6534-45. [PMID: 26814130 DOI: 10.1074/jbc.m115.696831] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Indexed: 11/06/2022] Open
Abstract
The small GTPase DiRas1 has tumor-suppressive activities, unlike the oncogenic properties more common to small GTPases such as K-Ras and RhoA. Although DiRas1 has been found to be a tumor suppressor in gliomas and esophageal squamous cell carcinomas, the mechanisms by which it inhibits malignant phenotypes have not been fully determined. In this study, we demonstrate that DiRas1 binds to SmgGDS, a protein that promotes the activation of several oncogenic GTPases. In silico docking studies predict that DiRas1 binds to SmgGDS in a manner similar to other small GTPases. SmgGDS is a guanine nucleotide exchange factor for RhoA, but we report here that SmgGDS does not mediate GDP/GTP exchange on DiRas1. Intriguingly, DiRas1 acts similarly to a dominant-negative small GTPase, binding to SmgGDS and inhibiting SmgGDS binding to other small GTPases, including K-Ras4B, RhoA, and Rap1A. DiRas1 is expressed in normal breast tissue, but its expression is decreased in most breast cancers, similar to its family member DiRas3 (ARHI). DiRas1 inhibits RhoA- and SmgGDS-mediated NF-κB transcriptional activity in HEK293T cells. We also report that DiRas1 suppresses basal NF-κB activation in breast cancer and glioblastoma cell lines. Taken together, our data support a model in which DiRas1 expression inhibits malignant features of cancers in part by nonproductively binding to SmgGDS and inhibiting the binding of other small GTPases to SmgGDS.
Collapse
Affiliation(s)
- Carmen Bergom
- From the Cancer Center, the Departments of Radiation Oncology,
| | - Andrew D Hauser
- From the Cancer Center, the Departments of Radiation Oncology, Pharmacology and Toxicology, and the Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016, and
| | | | - Patrick Gonyo
- From the Cancer Center, Pharmacology and Toxicology, and
| | | | | | - Alexis J Lawton
- the Department of Chemistry, Biochemistry Undergraduate Program, and
| | - Anne Frei
- From the Cancer Center, the Departments of Radiation Oncology
| | | | | | | | - Kathleen Noon
- the Mass Spectroscopy Facility for Proteomics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Carol A Fierke
- the Department of Chemistry, Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | | |
Collapse
|
12
|
Azoulay-Alfaguter I, Strazza M, Mor A. Chaperone-mediated specificity in Ras and Rap signaling. Crit Rev Biochem Mol Biol 2014; 50:194-202. [PMID: 25488471 DOI: 10.3109/10409238.2014.989308] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ras and Rap proteins are closely related small guanosine triphosphatase (GTPases) that share similar effector-binding domains but operate in a very different signaling networks; Ras has a dominant role in cell proliferation, while Rap mediates cell adhesion. Ras and Rap proteins are regulated by several shared processes such as post-translational modification, phosphorylation, activation by guanine exchange factors and inhibition by GTPase-activating proteins. Sub-cellular localization and trafficking of these proteins to and from the plasma membrane are additional important regulatory features that impact small GTPases function. Despite its importance, the trafficking mechanisms of Ras and Rap proteins are not completely understood. Chaperone proteins play a critical role in trafficking of GTPases and will be the focus of the discussion in this work. We will review several aspects of chaperone biology focusing on specificity toward particular members of the small GTPase family. Understanding this specificity should provide key insights into drug development targeting individual small GTPases.
Collapse
|
13
|
Cdc42p-interacting protein Bem4p regulates the filamentous-growth mitogen-activated protein kinase pathway. Mol Cell Biol 2014; 35:417-36. [PMID: 25384973 DOI: 10.1128/mcb.00850-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The ubiquitous Rho (Ras homology) GTPase Cdc42p can function in different settings to regulate cell polarity and cellular signaling. How Cdc42p and other proteins are directed to function in a particular context remains unclear. We show that the Cdc42p-interacting protein Bem4p regulates the mitogen-activated protein kinase (MAPK) pathway that controls filamentous growth in Saccharomyces cerevisiae. Bem4p controlled the filamentous-growth pathway but not other MAPK pathways (mating or high-osmolarity glycerol response [HOG]) that also require Cdc42p and other shared components. Bem4p associated with the plasma membrane (PM) protein, Sho1p, to regulate MAPK activity and cell polarization under nutrient-limiting conditions that favor filamentous growth. Bem4p also interacted with the major activator of Cdc42p, the guanine nucleotide exchange factor (GEF) Cdc24p, which we show also regulates the filamentous-growth pathway. Bem4p interacted with the pleckstrin homology (PH) domain of Cdc24p, which functions in an autoinhibitory capacity, and was required, along with other pathway regulators, to maintain Cdc24p at polarized sites during filamentous growth. Bem4p also interacted with the MAPK kinase kinase (MAPKKK) Ste11p. Thus, Bem4p is a new regulator of the filamentous-growth MAPK pathway and binds to general proteins, like Cdc42p and Ste11p, to promote a pathway-specific response.
Collapse
|
14
|
Schuld NJ, Vervacke JS, Lorimer EL, Simon NC, Hauser AD, Barbieri JT, Distefano MD, Williams CL. The chaperone protein SmgGDS interacts with small GTPases entering the prenylation pathway by recognizing the last amino acid in the CAAX motif. J Biol Chem 2014; 289:6862-6876. [PMID: 24415755 PMCID: PMC3945348 DOI: 10.1074/jbc.m113.527192] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 01/09/2014] [Indexed: 12/31/2022] Open
Abstract
Ras family small GTPases localize at the plasma membrane, where they can activate oncogenic signaling pathways. Understanding the mechanisms that promote membrane localization of GTPases will aid development of new therapies to inhibit oncogenic signaling. We previously reported that SmgGDS splice variants promote prenylation and trafficking of GTPases containing a C-terminal polybasic region and demonstrated that SmgGDS-607 interacts with nonprenylated GTPases, whereas SmgGDS-558 interacts with prenylated GTPases in cells. The mechanism that SmgGDS-607 and SmgGDS-558 use to differentiate between prenylated and nonprenylated GTPases has not been characterized. Here, we provide evidence that SmgGDS-607 associates with GTPases through recognition of the last amino acid in the CAAX motif. We show that SmgGDS-607 forms more stable complexes in cells with nonprenylated GTPases that will become geranylgeranylated than with nonprenylated GTPases that will become farnesylated. These binding relationships similarly occur with nonprenylated SAAX mutants. Intriguingly, farnesyltransferase inhibitors increase the binding of WT K-Ras to SmgGDS-607, indicating that the pharmacological shunting of K-Ras into the geranylgeranylation pathway promotes K-Ras association with SmgGDS-607. Using recombinant proteins and prenylated peptides corresponding to the C-terminal sequences of K-Ras and Rap1B, we found that both SmgGDS-607 and SmgGDS-558 directly bind the GTPase C-terminal region, but the specificity of the SmgGDS splice variants for prenylated versus nonprenylated GTPases is diminished in vitro. Finally, we present structural homology models and data from functional prediction software to define both similar and unique features of SmgGDS-607 when compared with SmgGDS-558.
Collapse
Affiliation(s)
- Nathan J Schuld
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jeffrey S Vervacke
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55414
| | - Ellen L Lorimer
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Nathan C Simon
- Department of Microbiology, Immunology, and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Andrew D Hauser
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Joseph T Barbieri
- Department of Microbiology, Immunology, and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Mark D Distefano
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55414
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.
| |
Collapse
|
15
|
Schuld NJ, Hauser AD, Gastonguay AJ, Wilson JM, Lorimer EL, Williams CL. SmgGDS-558 regulates the cell cycle in pancreatic, non-small cell lung, and breast cancers. Cell Cycle 2014; 13:941-52. [PMID: 24552806 DOI: 10.4161/cc.27804] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Oncogenic mutation or misregulation of small GTPases in the Ras and Rho families can promote unregulated cell cycle progression in cancer. Post-translational modification by prenylation of these GTPases allows them to signal at the cell membrane. Splice variants of SmgGDS, named SmgGDS-607 and SmgGDS-558, promote the prenylation and membrane trafficking of multiple Ras and Rho family members, which makes SmgGDS a potentially important regulator of the cell cycle. Surprisingly little is known about how SmgGDS-607 and SmgGDS-558 affect cell cycle-regulatory proteins in cancer, even though SmgGDS is overexpressed in multiple types of cancer. To examine the roles of SmgGDS splice variants in the cell cycle, we compared the effects of the RNAi-mediated depletion of SmgGDS-558 vs. SmgGDS-607 on cell cycle progression and the expression of cyclin D1, p27, and p21 in pancreatic, lung, and breast cancer cell lines. We show for the first time that SmgGDS promotes proliferation of pancreatic cancer cells, and we demonstrate that SmgGDS-558 plays a greater role than SmgGDS-607 in cell cycle progression as well as promoting cyclin D1 and suppressing p27 expression in multiple types of cancer. Silencing both splice variants of SmgGDS in the cancer cell lines produces an alternative signaling profile compared with silencing SmgGDS-558 alone. We also show that loss of both SmgGDS-607 and SmgGDS-558 simultaneously decreases tumorigenesis of NCI-H1703 non-small cell lung carcinoma (NSCLC) xenografts in mice. These findings indicate that SmgGDS promotes cell cycle progression in multiple types of cancer, making SmgGDS a valuable target for cancer therapeutics.
Collapse
Affiliation(s)
- Nathan J Schuld
- Department of Pharmacology and Toxicology; Medical College of Wisconsin; Milwaukee, WI USA
| | - Andrew D Hauser
- Department of Pharmacology and Toxicology; Medical College of Wisconsin; Milwaukee, WI USA
| | - Adam J Gastonguay
- Department of Pediatrics; Medical College of Wisconsin; Milwaukee, WI USA
| | - Jessica M Wilson
- Department of Pharmacology and Toxicology; Medical College of Wisconsin; Milwaukee, WI USA
| | - Ellen L Lorimer
- Department of Pharmacology and Toxicology; Medical College of Wisconsin; Milwaukee, WI USA
| | - Carol L Williams
- Department of Pharmacology and Toxicology; Medical College of Wisconsin; Milwaukee, WI USA
| |
Collapse
|
16
|
Hauser AD, Bergom C, Schuld NJ, Chen X, Lorimer EL, Huang J, Mackinnon AC, Williams CL. The SmgGDS splice variant SmgGDS-558 is a key promoter of tumor growth and RhoA signaling in breast cancer. Mol Cancer Res 2013; 12:130-42. [PMID: 24197117 DOI: 10.1158/1541-7786.mcr-13-0362] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Breast cancer malignancy is promoted by the small GTPases RhoA and RhoC. SmgGDS is a guanine nucleotide exchange factor that activates RhoA and RhoC in vitro. We previously reported that two splice variants of SmgGDS, SmgGDS-607, and SmgGDS-558, have different characteristics in binding and transport of small GTPases. To define the role of SmgGDS in breast cancer, we tested the expression of SmgGDS in breast tumors, and the role of each splice variant in proliferation, tumor growth, Rho activation, and NF-κB transcriptional activity in breast cancer cells. We show upregulated SmgGDS protein expression in breast cancer samples compared with normal breast tissue. In addition, Kaplan-Meier survival curves indicated that patients with high SmgGDS expression in their tumors had worse clinical outcomes. Knockdown of SmgGDS-558, but not SmgGDS-607, in breast cancer cells decreased proliferation, in vivo tumor growth, and RhoA activity. Furthermore, we found that SmgGDS promoted a Rho-dependent activation of the transcription factor NF-κB, which provides a potential mechanism to define how SmgGDS-mediated activation of RhoA promotes breast cancer. This study demonstrates that elevated SmgGDS expression in breast tumors correlates with poor survival, and that SmgGDS-558 plays a functional role in breast cancer malignancy. Taken together, these findings define SmgGDS-558 as a unique promoter of RhoA and NF-κB activity and a novel therapeutic target in breast cancer. IMPLICATIONS This study defines a new mechanism to regulate the activities of RhoA and NF-κB in breast cancer cells, and identifies SmgGDS-558 as a novel promoter of breast cancer malignancy.
Collapse
Affiliation(s)
- Andrew D Hauser
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226.
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Qi X, Zhi H, Lepp A, Wang P, Huang J, Basir Z, Chitambar CR, Myers CR, Chen G. p38γ mitogen-activated protein kinase (MAPK) confers breast cancer hormone sensitivity by switching estrogen receptor (ER) signaling from classical to nonclassical pathway via stimulating ER phosphorylation and c-Jun transcription. J Biol Chem 2012; 287:14681-91. [PMID: 22399296 DOI: 10.1074/jbc.m112.349357] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Estrogen receptor (ER) α promotes breast cancer growth by regulating gene expression through classical estrogen response element (ERE) binding and nonclassical (interaction with c-Jun at AP-1 sites) pathways. ER is the target for anti-estrogens such as tamoxifen (TAM). However, the potential for classical versus nonclassical ER signaling to influence hormone sensitivity is not known. Moreover, anti-estrogens frequently activate several signaling cascades besides the target ER, and the implications of these "off-target" signaling events have not been explored. Here, we report that p38γ MAPK is selectively activated by treatment with TAM. This results in both phosphorylation of ER at Ser-118 and stimulation of c-Jun transcription, thus switching ER signaling from the classical to the nonclassical pathway leading to increased hormone sensitivity. Unexpectedly, phosphorylation at Ser-118 is required for ER to bind both p38γ and c-Jun, thereby promoting ER relocation from ERE to AP-1 promoter sites. Thus, ER/Ser-118 phosphorylation serves as a central mechanism by which p38γ regulates signaling transduction of ER with its inhibitor TAM.
Collapse
Affiliation(s)
- Xiaomei Qi
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Hamel B, Monaghan-Benson E, Rojas RJ, Temple BRS, Marston DJ, Burridge K, Sondek J. SmgGDS is a guanine nucleotide exchange factor that specifically activates RhoA and RhoC. J Biol Chem 2011; 286:12141-8. [PMID: 21242305 PMCID: PMC3069418 DOI: 10.1074/jbc.m110.191122] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Revised: 01/06/2011] [Indexed: 11/06/2022] Open
Abstract
SmgGDS is an atypical guanine nucleotide exchange factor (GEF) that promotes both cell proliferation and migration and is up-regulated in several types of cancer. SmgGDS has been previously shown to activate a wide variety of small GTPases, including the Ras family members Rap1a, Rap1b, and K-Ras, as well as the Rho family members Cdc42, Rac1, Rac2, RhoA, and RhoB. In contrast, here we show that SmgGDS exclusively activates RhoA and RhoC among a large panel of purified GTPases. Consistent with the well known properties of GEFs, this activation is catalytic, and SmgGDS preferentially binds to nucleotide-depleted RhoA relative to either GDP- or GTPγS-bound forms. However, mutational analyses indicate that SmgGDS utilizes a distinct exchange mechanism compared with canonical GEFs and in contrast to known GEFs requires RhoA to retain a polybasic region for activation. A homology model of SmgGDS highlights an electronegative surface patch and a highly conserved binding groove. Mutation of either area ablates the ability of SmgGDS to activate RhoA. Finally, the in vitro specificity of SmgGDS for RhoA and RhoC is retained in cells. Together, these results indicate that SmgGDS is a bona fide GEF that specifically activates RhoA and RhoC through a unique mechanism not used by other Rho family exchange factors.
Collapse
Affiliation(s)
- Brant Hamel
- From the Departments of Biochemistry and Biophysics
| | | | | | - Brenda R. S. Temple
- From the Departments of Biochemistry and Biophysics
- the R. L. Juliano Structural Bioinformatics Core, and
| | | | - Keith Burridge
- Cell and Developmental Biology, and
- the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| | - John Sondek
- From the Departments of Biochemistry and Biophysics
- Pharmacology
- the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| |
Collapse
|
19
|
Berg TJ, Gastonguay AJ, Lorimer EL, Kuhnmuench JR, Li R, Fields AP, Williams CL. Splice variants of SmgGDS control small GTPase prenylation and membrane localization. J Biol Chem 2010; 285:35255-66. [PMID: 20709748 PMCID: PMC2975149 DOI: 10.1074/jbc.m110.129916] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ras and Rho small GTPases possessing a C-terminal polybasic region (PBR) are vital signaling proteins whose misregulation can lead to cancer. Signaling by these proteins depends on their ability to bind guanine nucleotides and their prenylation with a geranylgeranyl or farnesyl isoprenoid moiety and subsequent trafficking to cellular membranes. There is little previous evidence that cellular signals can restrain nonprenylated GTPases from entering the prenylation pathway, leading to the general belief that PBR-possessing GTPases are prenylated as soon as they are synthesized. Here, we present evidence that challenges this belief. We demonstrate that insertion of the dominant negative mutation to inhibit GDP/GTP exchange diminishes prenylation of Rap1A and RhoA, enhances prenylation of Rac1, and does not detectably alter prenylation of K-Ras. Our results indicate that the entrance and passage of these small GTPases through the prenylation pathway is regulated by two splice variants of SmgGDS, a protein that has been reported to promote GDP/GTP exchange by PBR-possessing GTPases and to be up-regulated in several forms of cancer. We show that the previously characterized 558-residue SmgGDS splice variant (SmgGDS-558) selectively associates with prenylated small GTPases and facilitates trafficking of Rap1A to the plasma membrane, whereas the less well characterized 607-residue SmgGDS splice variant (SmgGDS-607) associates with nonprenylated GTPases and regulates the entry of Rap1A, RhoA, and Rac1 into the prenylation pathway. These results indicate that guanine nucleotide exchange and interactions with SmgGDS splice variants can regulate the entrance and passage of PBR-possessing small GTPases through the prenylation pathway.
Collapse
Affiliation(s)
- Tracy J Berg
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | | | | | | | | | | | | |
Collapse
|
20
|
Hou SW, Zhi HY, Pohl N, Loesch M, Qi XM, Li RS, Basir Z, Chen G. PTPH1 dephosphorylates and cooperates with p38gamma MAPK to increase ras oncogenesis through PDZ-mediated interaction. Cancer Res 2010; 70:2901-10. [PMID: 20332238 DOI: 10.1158/0008-5472.can-09-3229] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Protein phosphatases are believed to coordinate with kinases to execute biological functions, but examples of such integrated activities, however, are still missing. In this report, we have identified protein tyrosine phosphatase H1 (PTPH1) as a specific phosphatase for p38gamma mitogen-activated protein kinase (MAPK) and shown their cooperative oncogenic activity through direct binding. p38gamma, a Ras effector known to act independent of its phosphorylation, was first shown to require its unique PDZ-binding motif to increase Ras transformation. Yeast two-hybrid screening and in vitro and in vivo analyses further identified PTPH1 as a specific p38gamma phosphatase through PDZ-mediated binding. Additional experiments showed that PTPH1 itself plays a role in Ras-dependent malignant growth in vitro and/or in mice by a mechanism depending on its p38gamma-binding activity. Moreover, Ras increases both p38gamma and PTPH1 protein expression and there is a coupling of increased p38gamma and PTPH1 protein expression in primary colon cancer tissues. These results reveal a coordinative oncogenic activity of a MAPK with its specific phosphatase and suggest that PDZ-mediated p38gamma/PTPH1 complex may be a novel target for Ras-dependent malignancies.
Collapse
Affiliation(s)
- Song-Wang Hou
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Loesch M, Zhi HY, Hou SW, Qi XM, Li RS, Basir Z, Iftner T, Cuenda A, Chen G. p38gamma MAPK cooperates with c-Jun in trans-activating matrix metalloproteinase 9. J Biol Chem 2010; 285:15149-15158. [PMID: 20231272 DOI: 10.1074/jbc.m110.105429] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Mitogen-activated protein kinases (MAPKs) regulate gene expression through transcription factors. However, the precise mechanisms in this critical signal event are largely unknown. Here, we show that the transcription factor c-Jun is activated by p38gamma MAPK, and the activated c-Jun then recruits p38gamma as a cofactor into the matrix metalloproteinase 9 (MMP9) promoter to induce its trans-activation and cell invasion. This signaling event was initiated by hyperexpressed p38gamma that led to increased c-Jun synthesis, MMP9 transcription, and MMP9-dependent invasion through p38gamma interacting with c-Jun. p38gamma requires phosphorylation and its C terminus to bind c-Jun, whereas both c-Jun and p38gamma are required for the trans-activation of MMP9. The active p38gamma/c-Jun/MMP9 pathway also exists in human colon cancer, and there is a coupling of increased p38gamma and MMP9 expression in the primary tissues. These results reveal a new paradigm in which a MAPK acts both as an activator and a cofactor of a transcription factor to regulate gene expression leading to an invasive response.
Collapse
Affiliation(s)
- Mathew Loesch
- Departments of Pharmacology and Toxicology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Hui-Ying Zhi
- Departments of Pharmacology and Toxicology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Song-Wang Hou
- Departments of Pharmacology and Toxicology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Xiao-Mei Qi
- Departments of Pharmacology and Toxicology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Rong-Shan Li
- Departments of Pathology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Zainab Basir
- Departments of Pathology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Thomas Iftner
- Section of Experimental Virology, Institute of Medical Virology and Epidemiology of Viral Diseases, University Hospital of Tübingen, Tübingen D-72076, Germany
| | - Ana Cuenda
- Departamento de Inmunología y Oncología, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain
| | - Guan Chen
- Departments of Pharmacology and Toxicology, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226; Research Services, the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee Medical College of Wisconsin, Milwaukee, Wisconsin 53226.
| |
Collapse
|
22
|
Expression of E-Cadherin, Cox-2, P53 and BCL-2 in Prostate Carcinomas: Correlation with Tumor Differentiation and Metastatic Potential. BIOTECHNOL BIOTEC EQ 2010. [DOI: 10.2478/v10133-010-0088-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|