GTPases


Aberrant regulation RAS and RHO GTPases is linked to a variety of disease states, including cancer, cardiovascular and neurological disorders.  RAS has been a topic of intense investigation, as oncogenic RAS mutations cause constitutive RAS activation and are prevalent in cancer.  We have a longstanding history studying RAS proteins.  In our earlier studies, we applied novel four dimensional nuclear magnetic resonance (NMR) approaches to determine the first solution structure of the RAS proto-oncogene.  Subsequently, my group at the University of North Carolina identified and solved the NMR solution structure of a domain (CRD) within the RAF kinase required for RAF kinase activation which stimulates the mitogen activated protein kinase cascade.  Our work has also elucidated how post-translational modifications of RAS, in particular, cysteine oxidation and ubiquitin modification.  Some of these modifications lead to RAS activation and tumorigenesis. Through these efforts, our lab developed novel chemical ligation and radical detection methods to characterize RAS post-translational modifications.  Our lab also showed that other members of the RAS superfamily (e.g., RHO GTPases) are regulated by these post-translational modifications, indicating conservation of these important regulatory mechanisms within the RAS superfamily of GTPases. We have recently extended these studies to investigate additional lysine modifications (acetylation, methylation) in RAS proteins. As RAS is a key anti-cancer target, we are characterizing various RAS/inhibitor complexes to facilitate drug discovery efforts.  In collaboration with the Der (UNC), Cox (UNC) and Counter (Duke) labs, we are evaluating how residue and site-specific mutation differences in RAS and RAC proteins lead to distinct signaling and tumorigenic signatures. Understanding these differences could lead to mutation specific anti-cancer therapies. We have recently initiated NMR structural, biophysical and biochemical studies on the heterotrimeric Gαi subunit.  In collaboration with the Bergmeier lab at UNC, we have recently elucidated the role of an exchange factor in membrane localization and activation of the RAP1b GTPase, which is key for platelet activation in response to injury.  Heterotrimeric G proteins are molecular switches that stimulate intracellular signaling cascades in response to activation of G-protein-coupled receptors (GPCRs) by extracellular stimuli. Our efforts here are centered on pH dependent changes that regulate Gα signaling as well as characterization of residue specific activating mutations found in cancer in collaboration with the Dohlman lab at UNC.

  1. Sarker M, Goliaei A, Golesi F, Poggi M, Cook AA, Khan MA, Temple BR, Stefanini L, Canault M, Bergmeier W, Campbell SL. (2020). Subcellular localization of Rap1 GTPase activator CalDAG-GEFI is orchestrated by interaction of its atypical C1 domain with membrane phosphoinositides. J Thromb Haemost, 18(3):693–705. doi:10.1111/jth.14687. * Journal cover.
  2. Hobbs G A, Baker N M, Miermont, A M, Thurman R, Pierobon M, Tran T H, Anderson A O, Waters A M, Diehl J N, Papke B, Hodge R G, Klomp J E, Goodwin C M, DeLiberty J M, Wang J, Ng R, Gautam P, Bryant K L, Esposito D, Campbell S L, Der, C. J. (2020). Atypical KRASG12R Mutant Is Impaired in PI3K Signaling and Macropinocytosis in Pancreatic Cancer. Cancer discovery, 10(1):104–123. https://doi.org/10.1158/2159-8290.CD-19-1006.
  3. Dohlman H G & Campbell S L (2019). Regulation of large and small G proteins by ubiquitination. J Biol Chem, 294(49): 18613–18623. https://doi.org/10.1074/jbc.REV119.011068
  4. Yoshino H, Yin G, Kawaguchi R, Popov K I, Temple B, Sasaki M, Kofuji S, Wolfe K, Kofuji K, Okumura K, Randhawa J, Malhotra A, Majd N, Ikeda Y, Shimada H, Kahoud E R, Haviv S, Iwase S, Asara J M, *Campbell S L, Sasaki A T (2019). Correction: Identification of lysine methylation in the core GTPase domain by GoMADScan. PloS one, 14(10): e0224443. https://doi.org/10.1371/journal.pone.0224443. *Joint corresponding authors
  5. Hsu AP, Donkó A, Arrington ME, Swamydas M, Fink D, Das A, Escobedo O, Bonagura V, Szabolcs P, Steinberg HN, Bergerson J, Skoskiewicz A, Makhija M, Davis J, Foruraghi L, Palmer C, Fuleihan RL, Church JA, Bhandoola A, Lionakis MS, Campbell S, Leto TL, Kuhns D, Holland SM. (2019). Dominant activating RAC2 mutation with lymphopenia, immunodeficiency and cytoskeletal defects. Blood, pii: blood-2018-11-886028. doi: 10.1182/blood-2018-11-886028.PMID: 30723080.
  6. Shellhammer JP, Morin-Kensicki E, Matson JP, Yin G, Isom DG, Campbell SL, Mohney RP, Dohlman HG. (2017). Amino acid metabolites that regulate G protein signaling during osmotic stress. PLoS Genet.,13(5): e1006829. doi: 10.1371/journal.pgen.1006829. eCollection 2017 May. PMID:28558063.
  7. Yin G, Kistler S, George SD, Kuhlmann N, Garvey L, Huynh M, Bagni RK, Lammers M, Der CJ, Campbell SL. (2017). A KRAS GTPase K104Q Mutant Retains Downstream Signaling by Offsetting Defects in Regulation. J Biol Chem., 292(11):4446-4456. Epub 2017 Jan 30. PMID: 2815417.
  8. Burd CE, Liu W, Huynh MV, Waqas MA, Gillahan JE, Clark KS, Fu K, Martin BL, Jeck WR, Souroullas GP, Darr DB, Zedek DC, Miley MJ, Baguley BC, Campbell SL, Sharpless NE. (2014). Mutation-Specific RAS Oncogenicity Explains N-RAS Codon 61 Selection in Melanoma. Cancer Discov, pii: CD-14-0729. PubMed PMID: 25252692.
  9. Baker R, Lewis SM, Sasaki AT, Wilkerson EM, Locasale JW, Cantley LC, Kuhlman B, Dohlman HG, Campbell SL. (2013). Site-specific monoubiquitination activates RAS by impeding GTPase-activating protein function. Nat Struct Mol Biol., (1):46-52. PubMed PMID: 23178454; PubMed Central PMCID: PMC3537887.
  10. Williams JG, Heo J, Pappu K, Campbell SL. (2003). A Novel Mechanism for Nitric Oxide Action and its Implications on the RAS Guanine Nucleotide Triphosphatase. Proc Natl Acad Sci USA, 100(11); 6376-6381.  PMID: 12740440.
  11. JG Williams, J Heo, K Pappu, SL Campbell. (2003). A Novel Mechanism for Nitric Oxide Action and its Implications on the RAS Guanine Nucleotide Triphosphatase. Proc Natl Acad Sci USA, 100(11); 6376-6381.  PMID: 12740440.
  12. Mott HR, Carpenter JW, Zhong S, Ghosh S, Bell RM, Campbell SL. (1996). The solution structure of the Raf-1 cysteine-rich domain: a novel RAS and phospholipid binding site. Proc Natl Acad Sci U S A., 93(16):8312-7. PubMed PMID: 8710867; PubMed Central PMCID: PMC38667.
  13. Laue ED, Boucher W, Domaille PJ, Campbell-Burk SL. (1992). Four Dimensional Triple Resonance NMR Methods for the Assignment of Backbone Nuclei in Proteins. J Am Chem Soc, 114, 2262-2264.
  14. Campbell-Burk SL, Domaille PJ, Starovasnik MA, Laue ED, Boucher W. (1992). Sequential Assignment of the Backbone Nuclei (1H, 15N, 13C) of H-Ras. GDP Using a Novel 4D NMR Strategy, J Biomol. NMR, 639-646.

Cell Adhesion Proteins


Our laboratory studies tumor suppressor (Vinculin) and tumor promoter (FAK, paxillin, palladin) proteins that control cell morphology and motility.  Deregulation of cell motility plays an important role in cell metastasis, often the leading cause of cancer deaths.  Our research efforts have elucidated protein-protein and protein-membrane interactions critical for regulated cell movement. Our group’s more recent studies of the cell adhesion protein, Vinculin, have focused on the Vinculin tail domain (Vt) and binding interactions with inositol phospholipids and actin. We have identified interaction sites important for phospholipid binding and membrane insertion, actin binding and actin bundling and characterized Vt variants that specially disrupt these protein-protein and protein-membrane interactions.  In collaboration with Clare Waterman’s group (NHLBI, NIH), super-resolution cellular microscopy approaches were employed to analyze the role of Vinculin in integrating F-actin and focal adhesion dynamics. We found that Vinculin functions as a molecular clutch to extract energy from the actin cytoskeleton and use it to move the whole cell across a substrate. We also found that coordinate binding of actin with talin promotes vinculin activation.  Actin binding to Vinculin also plays a key role in the sub-cellular distribution of Vinculin within focal adhesions. Although models for how Vinculin recognizes F-actin had been reported, our identification of a new actin binding interface on Vt, led us to examine alternative models for the Vt/actin complex.  We have recently obtained a cryo-electron microscopy (EM) reconstruction of the tail domains of both Vinculin and Metavinculin complexed to F-actin, in collaboration with the Alushin lab at NIH.  Our structure is consistent with the new or alternative actin interface proposed by our lab, and provides new insights into actin induced conformational changes in Vinculin that promote Vinculin dimerization and actin filament bundling.  Our current efforts are geared at understanding the structure of the actin-induced dimer, how the Vinculin dimer regulates actin reorganization, and how the splice variant Metavinculin coordinates with Vinculin to reorganize actin filaments.  As mutations and deletions in Metavinculin promote heart defects, we are characterizing how cardiomyopathy mutations alter actin organization in the absence and presence of Vinculin in vitro, and how expression of Metavinculin in MEFs alters cell adhesion and motility.  We are also studying how Vinculin and Metavinculin inserts in the membrane through specific interactions with the inositol phospholipid, PIP2, and how this interaction regulates localization, activation and focal adhesion turnover.

 

  1. Lee HT, Sharek L, O’Brien ET, Urbina FL, Gupton SL, Superfine R, Burridge K, Campbell SL. (2019) Vinculin and metavinculin exhibit distinct effects on focal adhesion properties, cell migration, and mechanotransduction. PLoS One, 14(9): e0221962. doi: 10.1371/journal.pone.0221962. PMID: 31483833; PMCID: PMC6726196.
  2. Krokhotin A, Sarker M, Sevilla EA,  Costantini LM,  Griffith JD,  *Campbell SL, Dokholyan NV (2019) Distinct Binding Modes of Vinculin Isoforms Underlie Their Functional Differences. Structure. 27(10):1527-1536.e3. doi: 10.1016/j.str.2019.07.013. Epub 2019 Aug 15. PMID:31422909; PMCID: PMC6774862. *Joint corresponding authors.
  3. Sarker M, Lee HT, Mei L, Krokhotin A, de Los Reyes SE, Yen L, Costantini LM, Griffith J, Dokholyan NV, Alushin GM, Campbell SL. (2019). Cardiomyopathy Mutations in Metavinculin Disrupt Regulation of Vinculin-Induced F-Actin Assemblies. J Mol Biol., pii: S0022-2836(19)30102-0. doi: 10.1016/j.jmb.2019.02.024. [Epub ahead of print] PMID: 30844403
  4. Thompson PM, Ramachandran S, Case LB, Tolbert CE, Tandon A, Pershad M, Dokholyan NV, Waterman CM, Campbell SL. (2017). A Structural Model for Vinculin Insertion into PIP2-Containing Membranes and the Effect of Insertion on Vinculin Activation and Localization. Structure., 25(2):264-275. Epub 2017 Jan 12. PMID: 28089450.
  5. Kim LY, Thompson PM, Lee HT,Pershad M, Campbell SL and Alushin GM. (2016). The Structural Basis of Actin Organization by Vinculin and Metavinculin. J Mol Biol., 428(1): 10-25.doi: 10.1016/j.jmb.2015.09.031. Epub 2015 Oct 20. PMID: 26493222.
  6. Lim, LY, Thompson, PM, Lee, HT, Pershad, M, Campbell, SL and Alushin, GM. The structural basis of actin organization by vinculin and metavinculin. (2016). Mol. Biol., 428:10-25.
  7. Thievessen I, Thompson PM, Berlemont S, Plevock KM, Plotnikov SV, Zemljic-Harpf A, Ross RS, Davidson MW, Danuser G, Campbell SL, Waterman CM. (2013). Vinculin-actin interaction couples actin retrograde flow to focal adhesions, but is dispensable for focal adhesion growth. J Cell Biol., 202(1):163-77.
  8. Shen K, Tolbert CE, Guilluy C, Swaminathan VS, Berginski ME, Burridge K, Superfine R, Campbell SL. (2011). The vinculin C-terminal hairpin mediates F-actin bundle formation, focal adhesion, and cell mechanical properties. J Biol Chem., 286 (52):45103-15. PubMed PMID: 22052910; PubMed Central PMCID: PMC3247952.