Faculty & Research

Larry Ruben, Ph.D. Professor Research Interests Ph.D.: University of Minnesota Postdoctoral training: Yale University

Office: 235-DLS Tel: 214.768.2321 Fax: 214.768.3955 Email: lruben@smu.edu Lab: 222-DLS Tel: 214.768.4097

Research Interests

Pathogenesis of African Trypanosomes/ Cellular-Signaling and Molecular Parasitology

African trypanosomiasis is caused by pathogenic protozoa that produce lethal infections in humans and livestock throughout sub-Saharan Africa. Over 60 million people in 36 countries are at risk of the disease with an estimated 300,000-500,000 deaths per year. In my lab, we study signal properties of Trypanosoma brucei. It is hypothesized that ablation of a signal or production of an inappropriate signal will be lethal to these organisms. While emphasis is placed upon the calcium regulatory network, our projects increasingly emphasize the signals and cytoskeletal elements responsible for cell division.

The research is greatly aided by the recently completed genome projects of the Tritryps (Trypanosoma brucei, Trypanosoma cruzi and Leishmania sp). Compared with the human host, the Trityps have notable deficiencies in their signal capabilities including the absence of trimeric G proteins, SH2 domains and serpentine receptors. In order to identify proteins that regulate cell division, inducible RNA interference and gene knockout are used. When the level of a putative regulatory protein is diminished, an evaluation of its role in cell cycle progression is made. Flow cytometry is used to analyze cell cycle progression. Yeast two-hybrid and endogenously expressed TAP-tags are used to identify binding partners within a pathway and laser scanning confocal microscopy is used to verify distribution of the candidate proteins during the cell cycle.

Recently we have used these methods to demonstrate that a RACK1 homologue (TRACK) from T. brucei is essential for completion of cytokinesis. In the absence of this homologue, trypanosomes initiate formation of a division furrow, but become stuck partway through the cleavage process. Rather than halt further cell division, the cells appear to lack appropriate checkpoints, and continue multiple rounds of partial cytokinesis. A movie of this novel phenotype is at: http://faculty.smu.edu/lruben. We are testing two hypotheses in an effort to explain the ability of TRACK to regulate cytokinesis. The first hypothesis is that TRACK modulates signal events on polysomes and in this way affects translation efficiency of some cell cycle proteins. In support of this hypothesis, we have recently shown that TRACK is indeed a component of monosomes and polysomes. The second hypothesis is that TRACK brings signal proteins to the cleavage furrow. TRACK partners are being sought by yeast two-hybrid and TAP-tag methods.

Other projects examine a trypanosome Aurora kinase that we report is required for chromatin segregation, division of the nucleus, and coupling of kinetoplast replication to that of the nucleus. Kinase assays demonstrated an ability of trypanosome Aurora kinase- 1 (TbAUK1) to phosphorylate recombinant histone H3 and H2B. We have used RNAi to knockdown Aurora kinase gene expression during the course of an infection in mice. Induction of RNAi with doxycycline caused the parasitemia to fall and allowed the mice to survive. These data provide proof of concept that the trypanosome Aurora kinase is a potential therapeutic target.

Along with the study of kinases that drive the cell division cycle, we have also identified cell cycle regulatory protein phosphatases. Notable among them is a PP2A family member whose activity is essential to initiate the onset of cytokinesis. Additonally, there are two PP2B (calcineurin) genes in T. brucei. Although their functions are unknown, each interacts differently with calcineurin B, calmodulin and FKBP12. Overall, these projects help define the regulatory proteins required for cell division and identify novel targets for the development of new therapies.

Left: TRACK is found in monosome and polysome fractions in T. brucei.
Right: Molecular model of a small molecule inhibitor bound to the active site of trypanosome Aurora kinase-1 (model provided by John Wise, SMU).

Selected Publications

Jetton, N., Rothberg, K.G. and Ruben, L. An aurora kinase from Trypanosoma brucei. Phosphorylates histones H3 and H2B, and is sensitive to small-molecule inhibitors (Submitted)

Rothberg, K. G., Burdette, Pfannstiel, J., D., Jetton, N., Singh, R. and Ruben, L. (2006) The RACK1 homologue from Trypanosoma brucei is required for onset and progression of cytokinesis. J. Biol. Chem. 281, 9781-9790.

Ruben, L., Kelly, J.M. and Chakrabarti, D. (2003) Cellular Signaling. In: Molecular and Medical Parasitology (Marr, J.J, Nilsen, T.W. and Komuniecki, R.,W. eds). pp. 241-276. Academic Press, UK

Ridgley, E; L. and Ruben, L. (2001) Phospholipase from Trypanosoma brucei releases arachidonic acid by sequential sn-1 and sn-2 deacylation of phospholipids. Mol. Biochem. Parasitol. 114, 29-40.

Ridgley, E.L., Webster, P., Patton, C.L., and Ruben, L. (2000) Calmodulin-binding properties of the paraflagellar rod complex from Trypanosoma brucei Mol. Biochem. Parasitol. 109, 195-201.

Parsons, M. and Ruben, L. (2000) Pathways involved in environmental sensing in trypanosomatids. Parasitol. Today. 16, 58-64.

Ridgley, E.L., Xiong, Z.-H. and Ruben, L. (1999) Reactive oxygen species activate a calcium-dependent cell death pathway in Trypanosoma brucei. Biochem. J. 340, 33-40.

Eintracht, J., Maathai, R., Mellors, A. and Ruben, L. (1998) Calcium entry in Trypanosoma brucei is regulated by phospholipase A2 and arachidonic acid. Biochem. J. 336, 659-666.

Xiong, Z.-H. and Ruben, L. (1998) Trypanosoma brucei: The dynamics of calcium movement between the cytosol, nucleus and mitochondrion of intact cells. Exp. Parasitol. 88, 231-239.

Xiong, Z.-H., Ridgley, E.L., Enis, D., Olness, F. and Ruben, L. (1997) Selective transfer of calcium from an acidic compartment to the mitochondrion of Trypanosoma brucei: Measurements with targeted aequorins. J. Biol. Chem. 272, 31022-31028.

Xiong, Z.-H. and Ruben, L. (1996) Nuclear calcium flux in Trypanosoma brucei can be quantified with targeted aequorin. Mol. Biochem. Parasitol. 83, 57-67.

Ruben, L., Akins, C.D., Haghighat, N.G., and Xue, L. (1996) Calcium influx in Trypanosoma brucei can be induced by amphiphilic peptides and amines. Mol. Biochem. Parasitol. 81, 191-200.

Ridgley, E.L., Xiong, Z., Kaur, K.J. and Ruben, L. (1996) Genomic organization and expression of elongation factor-1 genes in Trypanosoma brucei. Mol. Biochem. Parasitol. 79, 119-123.

Wu, Y., DeFord, J., Benjamin, R., Lee, M.G.-S., and Ruben, L. (1994) The gene family of EF-hand calcium-binding proteins from the flagellum of Trypanosoma brucei. Biochem. J. 304, 833-841.

Kaur, K. and Ruben, L. (1994) Protein translation elongation factor-1 from Trypanosoma brucei binds calmodulin. J. Biol. Chem. 269, 23045-23050.

Salmon, D., Geuskens, M., Hanocq, F., Hanocq-Quertier, J., Nolan, D., Ruben, L., and Pays, E. (1994) A novel heterodimeric transferrin receptor encoded by a pair of VSG expression site-associated genes in Trypanosoma brucei. Cell 78, 75-86.

Wu, Y., Haghighat, N.G., and Ruben, L. (1992) The predominant calcimedins from Trypanosoma brucei comprise a family of flagellar EF-hand calcium-binding proteins. Biochem. J. 287, 187-193.

Haghighat, N.G. and Ruben, L. (1992) Purification of novel calcium-binding proteins from Trypanosoma brucei: properties of 22-, 24-, and 38-kilodalton proteins. Mol. Biochem. Parasitol. 51, 99-110.

Ruben, L. and Akins, C.D. (1992) Trypanosoma brucei: The tumor promoter thapsigargin stimulates calcium release from an intracellular compartment in slender bloodstream forms. Exp. Parasitol. 74, 332-339.

Ruben, L., Hutchinson, A., and Moehlman, J. (1991) Calcium homeostasis in Trypanosoma brucei: Identification of a pH sensitive non-mitochondrial calcium pool. J. Biol. Chem. 266, 24351-24358.

Ruben, L., Ridgley, E., Chan, E., and Haghighat, N.G. (1991) Variable surface glycoprotein from Trypanosoma brucei strain YTat1.1 contains a latent calmodulin-binding domain. Mol. Biochem. Parasitol. 46:123-136.

Ruben, L., Haghighat, N., and Campbell, A. (1990) Cyclical differentiation of Trypanosoma brucei involves changes in the cellular complement of calmodulin-binding proteins. Exp. Parasitol. 70, 144-153.

Ruben, L. (1987) Identification of a developmentally regulated calcium-binding protein in Trypanosoma brucei. J. Protozool. 34, 367-370.

Rice, H., Ruben, L., Gould, S., Njogu, A.R., and Patton, C.L. (1987) Phenothiazines in murine African trypanosomiasis. Trans. R. Soc. Trop. Med. Hyg. 81, 932.

Ruben, L. and Patton, C.L. (1985) Comparative structural analysis of calmodulins from Trypanosoma brucei, T. congolense, T. vivax, Tetrahymena thermophila and bovine brain. Mol. Biochem. Parasitol. 17, 331-341.

Ruben, L. and Patton, C.L. (1985) Antibodies to calmodulin during experimental Trypanosoma brucei rhodesiense infections in rabbits. Immunol. 56, 227-233.

Tschudi, C., Young, A.S., Ruben, L., Patton, C.L., and Richards, F.F. (1985) Calmodulin genes in trypanosomes are tandemly repeated and produce multiple mRNAs with a common 5' leader sequence. Proc. Natl. Acad. Sci. USA 82, 3998-4002.

Ruben, L., Egwuagu, C., and Patton, C.L. (1983) African trypanosomes contain calmodulin which is distinct from host calmodulin. Biochim. Biophys. Acta 758, 104-113.

Ruben, L., Lageson, J., Hyzy, R., and Hooper, A.B. (1982) Culture growth cycle dependent overproduction and storage of protoporphyrin IX in Tetrahymena: Effect of heavy metals. J. Protozool. 29, 233-238.

Ruben, L. and Hooper, A.B. (1982) Dependence of nucleus-directed ribosomal RNA synthesis upon mitochondrial protein synthesis in Tetrahymena. Mol. Cell. Biol. 2, 508-516.

Ruben, L. and Rasmussen, H. (1981) Phenothiazines and related compounds disrupt mitochondrial energy production by a calmodulin-independent reaction. Biochim. Biophys. Acta 637, 414-422.

Ruben, L. and Hooper, A.B. (1978) Chloramphenicol-induced growth arrest in animal cells. Presence of non-adenylate mediated feedback control in Tetrahymena. J. Biol. Chem. 253, 7262-7268.

Support

ONGOING SUPPORT

2004-2009

(Principle Investigator) NIH-NIAID RO1: TRACK Regulates Cytokinesis in Trypanosoma brucei

COMPLETED SUPPORT

1998-2004	(Principle Investigator) NIH-NIAID RO1: Eicosanoic Acids and Calcium in African Trypanosomes
1994-1997	(Principle Investigator) NIH-NIAID RO1: Calcium Pathways in African Trypanosomes.
1995-1996	(Principle Investigator) CMIT-Culpeper Faculty Instructional Technology Grant: Interactive Computer-Based Instruction in Cell Biology.
1991-1994	(Principle Investigator) UNDP/WORLD BANK/WHO Special Programme for Research and Training in Tropical Diseases. Calcium Antagonists and Treatment of African Trypanosomiasis.
1989	(Co-Principal Investigator) The Biological Instrumentation Program, NSF; Purchase of a Transmission Electron Microscope and Accessory Equipment for Image Processing and Analysis.
1988-1990	(Principal Investigator) Texas Advanced Technology Program, Molecular Characterization of the Transferrin Receptor from African Trypanosomes: A Possible Vaccine Candidate.
1987-1992	(Principal Investigator) NIH-NIAID RO1: Molecular Biology of Calcium Pathways in African Trypanosomes.
1985-1987	(Principal Investigator) Young Investigator's Award, NIH-NIAID; Calcium-binding Proteins in African Trypanosomes.

OTHER LINKS TO TRYPANOSOMES

Trypanosome Genome:
http://www.geneDB.org

World Health Organization:
http://www.who.int/tdr
http://www.who.int/tdr/diseases/tryp/default.htm

Food and Agriculture Organization of the UN
http://www.fao.org/ag/againfo/programmes/en/paat/home.html

Links to Other Labs
http://www.biochem.uiowa.edu/donelson/Trypanosome%20links.htm
http://tryps.rockefeller.edu

Education

1970-1972	University of California, Los Angeles, CA
1972-1974	B.A. Zoology University of California, Berkeley, CA
1974-1979	Ph.D. Cell Biology University of Minnesota, St. Paul, MN Mitochondrial and nuclear interactions in the ciliated protozoan Tetrahymena.

Professional Experience

1979-1982	Post-doctoral Associate: Department of Internal Medicine, Yale University, New Haven, CT (with Howard Rasmussen). Calcium and calmodulin regulatory pathways.
1982-1984	Post-doctoral Fellow: Department of Epidemiology and Public Health, Yale University, New Haven, CT (with Curtis Patton) Calcium signals in Trypanosoma brucei.
March-August 1983	Visiting Scientist: International Laboratory for Research in Animal Diseases, Nairobi, KENYA
1984-1986	Associate Research Scientist: Department of Epidemiology and Public Health, Yale University, New Haven, CT
1986-1992	Assistant Professor: Department of Biology, Southern Methodist University, Dallas, TX
1992-1998	Associate Professor: Department of Biology, Southern Methodist University, Dallas, TX
January-April 1993	Visiting Scientist Free University of Brussels, Belgium (Sabbatical leave with Etienne Pays)
1999-Present	Professor: Department of Biology, Southern Methodist University, Dallas, TX
2002-2006	Chair, Department of Biology, Southern Methodist University, Dallas, TX

Review Panels

2004-Present	NIH: PTHE Study Section, NIAID; ad hoc Reviewer.
2001-2004	NIH TMP Study Section, NIAID; Panel Member.
1998-2001	NIH TMP and Vector Biology Visiting Review Panel Member.
1994-1996	NSF Review Panel Member: Academic Research Infrastructure (ARI)

Additional Ad Hoc Grant Review (1995-Present)

• NIH ad hoc Study Section: AIDS Related Research
• NSF: Multi-User Biological Equipment Grants
• Massachusetts Agriculture Experimental Station Grants, U. Mass., Amherst Medical Research Council, UK
• NIH-NIAID ad hoc Review Panel for AIDS Study Section
• NSF: Signal Transduction and Regulation Grants
• NSF: reviewer for the RIMI Program
• MRC: reviewer for the Medical Research Council; England

Awards and Recognition

• HOPE Professor of the Year (2006)
• The SMU Bridge Building Committee Student Affairs Award (2004)
• Orientation Leadership Institute Outstanding Faculty Award (2004) (Inaugural Award)
• United Methodist Church Scholar /Teacher of the Year Award (2004)
• Honoring Our Professors Experience (HOPE) Award (2003)
• SMU Faculty Good Citizen Award (2003)
• Willis M. Tate Award, Outstanding Faculty Member (1999-2000)
• SMU Student Senate Outstanding Faculty/Staff Award (1999)
• "M" Award for Service (1995)