Research Personnel Publications Databases Facilities Services Training Seminars
The University of Georgia Complex Carbohydrate Research Center
Employment CCRC History Location Links Centers
 
Personnel
 Tenure-Track Faculty
 Administrative Staff
 Non Tenure-Track Faculty
 Science Staff
 Postdoctoral Research Associates
 Graduate Students
 Undergraduate Students
Tenure-Track Faculty
Robert Haltiwanger
GRA Eminent Scholar in Biomedical Glycoscience


Role of protein glycosylation in signal transduction and protein folding

E-mail: rhalti@uga.edu
Telephone: 706-542-4151
Fax: 706-542-4412

Short Biography
Research Interests
Publications

Short Biography:
Dr. Haltiwanger received his B.S. in Biology (1980) and Ph.D. in Biochemistry (1986) from Duke University. He went on to do postdoctoral work at Johns Hopkins University School of Medicine, and took his first independent position as an Assistant Professor in the Department of Biochemistry and Cell Biology at Stony Brook University (1991). He rose through the ranks to full Professor and served as Chair of that Department for 8 years. He moved to the CCRC in 2015 as the GRA Eminent Scholar in Biomedical Glycosciences. He has served as President of the Society for Glycobiology, Chair of the Glycobiology Gordon Conference, and currently serves as Editor-in-Chief of the journal Glycobiology.

To Top

Research Interests:
Glycobiology is a relatively young field that focuses on examining the biological effects of modifying proteins and lipids with carbohydrates. Glycans provide incredible structural diversity to biological systems, offering the potential to alter function in a wide variety of ways, but also bringing significant technical challenges for structural analysis. Advances in methodologies to examine these structures has brought significant insight into functions for glycans in a wide variety of biological contexts over the past decade, causing rapid growth and interest in the field. My laboratory focuses on the role of carbohydrate modifications on proteins, especially as they affect cellular communication events. Protein glycosylation exists in two major forms: N-linked, referring to glycans linked to protein through the amide nitrogen of asparagine residues, and O-linked, where the glycans are linked through the hydroxyl groups of serine or threonine. O-Glycans are divided into subclasses based on the carbohydrate linked directly to the serine or threonine. The subclasses that we focus on are called O-fucose and O-glucose. All of the projects in the laboratory deal with learning more about these forms of glycosylation. Several are discussed in more detail below.

Regulation of Notch Signaling by O-fucose and O-glucose:

The Notch protein plays a key role in communication between cells. It functions at the surface of the cell where it binds to ligands expressed on adjacent cells (e.g. Delta, Serrate, Jagged), resulting in its activation. Such communication between cells is essential for proper development of metazoans, and defects in Notch function result in a number of human diseases, including severe mental and physical retardation, congenital heart defects, vascular defects leading to stroke and dementia, and several forms of cancer. A clear understanding of how Notch functions is essential to develop therapies for these diseases.

We have demonstrated that O-fucose and O-glucose glycans modify the Epidermal Growth Factor-like (EGF) repeats of the Notch extracellular domain. We have identified the enzymes responsible for addition of the O-fucose, protein O-fucosyltransferase 1 (POFUT1) and O-glucose, protein O-glucosyltransferase 1 (POGLUT1) to Notch. Elimation of either of these enzymes in mice or flies results in severe Notch phenotypes. Thus, the O-fucose and O-glucose modifications are essential for proper Notch function. Several studies suggest that the O-fucose modifications are important for Notch to be able to bind to its ligands. O-Glucose modifications do not affect ligand binding so affect Notch function through some other mechanism. We are currently investigating in molecular detail how O-fucose and O-glucose affect Notch.

Both O-fucose and O-glucose are elongated by other sugars, and this elongation regulates Notch activity. We have demonstrated that the Fringe protein is a glycosyltransferase that adds an N-acetylglucosamine (GlcNAc), to O-fucose on Notch. Fringe modification modulates Notch function, increasing and/or decreasing its response to ligands depending on the circumstances. These results demonstrated that cellular communication through the Notch protein can be regulated by altering the carbohydrate structures (O-fucose structures) on Notch. This was a very important finding for the field of Glycobiology, as it was a clear example of a principle proposed over 50 years ago, that carbohydrate modifications on cell surface receptors could modulate their function. We know that Fringe-mediated changes in O-fucose structures alter Notch-ligand binding, and we are examining at a molecular level how this occurs.

O-Glucose is elongated by xylose residues, and in collaboration with Dr. Hamed Jafar-Nejad’s group we have shown that elongation of O-glucose inhibits Notch activity. We are currently examining the molecular mechanisms for how O-glucose modifications affect Notch activity.

O-fucose modifications on Thrombospondin Type 1 Repeats:

O-Fucose modifications also exist in a different protein context called a thrombospondin type 1 repeat (TSR). TSRs are found in dozens of cell-surface and secreted proteins, and most are predicted to be modified with O-fucose. We have identified the enzyme responsible for adding O-fucose to TSRs, protein O-fucosyltransferase 2 (POFUT2), a distant homolog of POFUT1. Elimination of POFUT2 in mice results in embryonic lethality just after gastrulation. We are currently examining which POFUT2 targets are responsible for this lethality.

We have also identified the enzyme that adds a glucose residue to the O-fucose on TSRs to generate a Glucose-β1,3-Fucose disaccharide called β3-glucosyltransferase (B3GLCT). Mutations in B3GLCT result in a rare developmental disorder known as Peter’s Plus Syndrome (PPS). PPS patients display a number of developmental abnormalities including eye defects, short stature, brachydactyly, cleft palate, and unusual craniofacial features. Our recent studies suggest that both POFUT2 and B3GLCT are required for proper folding of TSRs. Thus, loss of either enzyme causes folding defects in proteins containing TSRs. We are currently pursuing how addition of these sugars affects the folding of the TSRs.

To Top

Publications: Author's Last Name: Haltiwanger

Journal Articles
Book Chapters are listed at the bottom of this page.

S Kakuda, RS Haltiwanger. 2017. Deciphering the Fringe-mediated Notch Code: Identification of activating and inhibiting sites allowing discrimination between ligands. Dev Cell 40: 193-201. PMID:28089369

D Hubmacher, M Schneider, SJ Berardinelli, H Takeuchi, B Willard, DP Rinhardt, RS Haltiwanger, SS Apte. 2017. Unusual life cycle and impact on microfibril assembly of ADAMTS17, a secreted metalloprotease mutated in genetic eye disease. Sci Rep 7: 41871-. PMID:28176809

MO Sheikh, SM Halmo, S Patel, D Middleton, H Takeuchi, CM Schafer, CM West, RS Haltiwanger, FY Avci, KW Moremen, L Wells. 2017. Rapid screening of sugar-nucleotide donor specificities of putative glycosyltransferases. Glycobiology 27: 206-212. PMID:28177478

VC Luca, BC Kim, C Ge, S Kakuda, D Wu, M Roein-Peikar, RS Haltiwanger, C Zhu, T Ha, KC Garcia, . 2017. Notch-Jagged complex structure implicates a catch bond in tuning ligand sensitivity. Science 355: 1320-1324. PMID:28254785

VC Luca, BC Kim, C Ge, S Kakuda, D Wu, M Roein-Peikar, RS Haltiwanger, C Zhu, T Ha, KC Garcia, . 2017. Notch-Jagged complex structure implicates a catch bond in tuning ligand sensitivity. Science 355: 1320-1324. PMID:28254785

MO Sheikh, SM Halmo, S Patel, D Middleton, H Takeuchi, CM Schafer, CM West, RS Haltiwanger, FYI Avci, KW Moremen, L Wells. 2017. Rapid screening of sugar-nucleotide donor specificities of putative glycosyltransferases. Glycobiology Mar 1; 27(3): 206-212. PMID:28302723

S.M. Thakurdas, M.F. Lopez, S. Kakuda, R. Fernandez-Valdivia, N. Zarrin-Khameh, R.S. Haltiwanger, H. Jafar-Nejad. 2016. Jagged1 heterozygosity in mice results in a congenital cholangiopathy which is reversed by concomitant deletion of one copy of Poglut1 (Rumi). Hepatology 63: 550-565. PMID:26235536

E Servian-Morilla, H Takeuchi, TV Lee, J Clarimon, F Mavillard, E Area-Gomez, E Rivas, JL Nieto-Gonzalez, MC Rivero, M Cabrera-Serrano, L Gomez-Sanchez, JA Martinez-Lopez, B Estrada, C Marquez, Y Morgado, X Suarez-Calvet, G JPita, A Bigot, E Gallardo, R Fernandez-Chachon, M Hirano, RS Haltiwanger, H Jara-Nejad, C Parada. 2016. A POGLUT1 mutation causes a muscular dystrophy with reduced Notch signaling and satellite cell loss. EMBO Mol Med 8: 1289-1309. PMID:27807076

J Dubail, D Vasudevan, SE Earp, MW Jenkins, RS Haltiwanger, SS Apte. 2016. Impaired ADAMTS9 secretion: A potential mechanism for eye defects in Peters Plus Syndrome. Sci Rep 6: 33974-. PMID:27687499

H Yu, H Takeuchi, M Takeuchi, Q Liu, J Kantharia, RS Haltiwanger, H Liu. 2016. Structural analysis of Notch-regulating Rumi reveals basis for pathogenic mutations. Nat Chem Biol 12: 735-740. PMID:27428513

B Benz, S Nandadasa, M Takeuchi, RC Grady, H Takeuchi, RK LoPilato, S Kakuda, RPT Somerville, SS Apte, RS Haltiwanger, BC Holdener. 2016. Genetic and biochemical evidence that gastrulation defects in Pofut2 mutants result from defects in ADAMTS9 secretion. Dev Biol 416: 111-122. PMID:27297885

BM Harvey, NA Rana, H Moss, J Leonardi, H Jafar-Nejad, RS Haltiwanger. 2016. Mapping Sites of O-Glycosylation and Fringe Elongation on Drosophila Notch. J Biol Chem 291: 16348-16360. PMID:27268051

J Valero-Gonzalez, C Leohhard-Melief, E Lira-Naverrete, G Jimenz-Oses, C Hernandez-Ruiz, MC Pallares, I Yruela, D Vasudevan, A Lostao, F Corzana, H Takeuchi, RS Haltiwanger, R Hurtado-Guerrero. 2016. A proactive role of water molecules in acceptor recognition by protein O-fucosyltransferase 2. Nat Chem Biol 12: 240-246. PMID:26854667

D. Vasudevan, H. Takeuchi, S.S. Johar, E. Majerus, R.S. Haltiwanger. 2015. Peters plus syndrome mutations disrupt a noncanonical ER quality-control mechanism. Curr. Biol. 25: 286-295. PMID:25544610

H Yu, M Takeuchi, J LeBarron, J. Kantharia, E London, H. Bakker, RS Haltiwanger, H. Li, H. Takeuchi. 2015. Notch-modifying xylosyltransferase structures support an SNi-like retaining mechanism. Nat Chem Biol 11: 847-854. PMID:26414444

N Ramkumar, BM Harvey, JD Lee, HL Alcorn, NF Silva-Gagliardi, CJ McGlade, TH Bestor, J Wijnholds, RS Haltiwanger, KV Anderson. 2015. Proten O-Glucosyltransferase 1 (POGLUT1) Promotes Mouse Gastrulation through Modification of the Apical Polarity Protein CRUMBS2. PLoS Genetics 11(10): e1005551-. PMID:26496195

J. Muller, N.A. Rana, K. Serth, S. Kakuda, R.S. Haltiwanger, A. Gossler. 2014. O-Fucosylation of the Notch ligand mDLL1 by POFUT1 is dispensible for ligand function. PLoS One 9: e88571-. PMID:24533113

P. Taylor, H. Takeuchi, D. Sheppard, C. Chillakuri, SM Lea, R.S. Haltiwanger, P.A. Handford. 2014. Fringe-mediated extension of O-linkedfucose in the ligand-binding region of Notch1 increases binding to mammalian Notch ligands. Proc. Natl. Acad. Sci. USA 111: 7290-7295. PMID:24803430

A.R. Haltom, T.V. Lee, B.M. Harvey, J. Leonardi, Y.J. Chen, Y. Hong, R.S. Haltiwanger, H. Jafar-Nejad. 2014. The protein O-glycosyltransferase Rumi modifies eyes shut to promote rhabdomere separation in Drosophila. PLoS Genet. 10: e1004795-. PMID:25412384

E. Al-Shareffi, J.-L. Chaubard, C. Leonhard-Melief, S.-K. Wang, C.-H. Wong, R.S. Haltiwanger. 2013. 6-Alkynyl fucose is a bioorthogonal analogue for O-fucosylation of epidermal growth factor-like repeats and thrombospondin type-1 repeats by protein O-fucosyltransferases 1 and 2. Glycobiology 23: 188-198. PMID:23045360

T.V. Lee, M.K. Sethi, J. Leonardi, N.A. Rana, F.F.R. Buettner, R.S. Haltiwanger, H. Bakker, H. Jafar-Nejad. 2013. Negative regulation of Notch signaling by xylose. PLoS Genet. 9: e1003547-. PMID:23754965

M.K. Sethi, F.F>R. Buettner, A. Ashikov, V.B. Krylov, H. Takeuchi, N.E. Nifantiev, R.S. Haltiwanger, R. Gerardy-Schahn, H. Bakker. 2012. Molecular cloning of a xylosyltransferase that transfer the second xylose to O-glucosylated epidermal growth factor repeats of Notch. J. Biol. Chem. 287: 2739-2748. PMID:22117070

H. Takeuchi, J. Kantharia, M.K. Sethi, H. Bakker, R.S. Haltiwanger. 2012. Site-specific O-glucosylation of the epidermal growth factor-like (EGF) repeats of Notch: Efficiency of glycosylation is affected by proper folding and amino acid sequence of individual EGF repeats. J. Biol. Chem. 287: 33934-33944. PMID:22872643

S. Yamamoto, W.-L. Charng, N.A. Rana, S. Kakuda, M. Jaiswal, V. Bayat, B. Xiong, K. Zhang, H. Sandoval, G. David, H. Wang, R.S. Haltiwanger, H.J. Bellen. 2012. A mutation in EGF repeat-8 of Notch discriminates between Serrate/Jagged and Delta family ligands. Science 338: 1229-1232. PMID:23197537

R. Fernandez-Valdivia, H. Takeuchi, A. Samarghandi, M. Lopez, J. Leonardi, R.S. Haltiwanger, H. Jafar-Nejad. 2011. Regulation of the mammalian Notch signaling and embryonic development by the protein O-glucosyltransferase Rumi. Development 138: 1925-1934. PMID:21490058

N.A. Rana, A. Nita-Lazar, H. Takeuchi, S. Kakuda, K.B. Luther, R.S. Haltiwanger. 2011. O-Glucose trisaccharide is present at high but variable stoichiometry at multiple sites on mouse Notch1. J. Biol. Chem. 286: 31623-31637. PMID:21757702

H. Takeuchi, R.C. Fernandez-Valdivia, D.S. Caswell, A. Nita-Lazar, N.A. Rana, T. Garner, T. Weldegheorghis, M.A. Macnaughtan, H. Jafar-Nejad, R.S. Haltiwanger. 2011. Rumi functions as both a protein O-glucosyltransferase and a protein O-xylosyltransferase. Proc. Natl. Acad. Sci. USA 108: 16600-16605. PMID:21949356

M.K. Sethi, F.F.R. Buettner, V.B. Krylov, H. Takeuchi, N.E. Nifantiev, R.S. Haltiwanger, R. Gerardy-Schahn, H. Bakker. 2010. Identification of glycosyltransferase 8 family members as xylosyltransferases actin on O-glucosylated Notch EGF repeats. J. Biol. Chem. 285: 1582-1585. PMID:19940119

J. Du, H. Takeuchi, C. Leonhard-Melief, K.R. Shroyer, M. Dlugosz, R.S. Haltiwanger, B.C. Holdener. 2010. O-Fucosylation of thrombospondin type 1 repeats restricts epithelial to mesenchymal transition (EMT) and maintains epiblast pluripotency during mouse gastrulation. Dev. Biol. 346: 25-38. PMID:20637190

K.B. Luther, H. Schindelin, R.S. Haltiwanger. 2009. Structural and mechanistic insights into Lunatic Fringe from a kinetic analysis of enzyme mutants. J. Biol. Chem. 284: 3294-3305. PMID:19028689

H. Bakker, T. Oka, A. Ashiko, A. Yadav, M. Berger, N.A. Rana, X. Bai, Y. Jigami, R.S. Haltiwanger, J.D. Esko, R. Gerardy-Schahn. 2009. Functional UDP-xylose transport across the ER/Golgi membrane in a Chinese hamster ovary cell mutant defective in UDP-xylose synthase. J. Biol. Chem. 284: 2576-2583. PMID:19028698

L.W. Wang, C. Leonhard-Melief, R.S. Haltiwanger, S.S. Apte. 2009. Post-translational modification of thrombospondin type-1 repeats in ADAMTS-like 1/punctin-1 by C-mannosylation of tryptophan. J. Biol. Chem. 284: 30004-30015. PMID:19671700

M. Acar, H. Jafar-Nejad, H. Takeuchi, A. Rajan, D. Ibrani, N.A. Rana, H. Pan, R.S. Haltiwanger, H.J. Bellen. 2008. Rumi is a CAP10 domain glycosyltransferase that modifies Notch and is required for Notch signaling. Cell 132: 247-258. PMID:18243100

H.O. Ishikawa, H. Takeuchi, R.S. Haltiwanger, K.D. Irvine. 2008. Four-jointed is a Golgi kinase that phosphorylates a subset of cadherin domains. Science 321: 401-404. PMID:18635802

L.M. Ricketts, M. Dlugosz, K.B. Luther, R.S. Haltiwanger, E.M. Majerus. 2007. O-fucosylation is required for ADAMTS13 secretion. J. Biol. Chem. 282: 17014-17023. PMID:17395589

L.W. Wang, M. Dlugosz, R.P. Somerville, M. Raed, R.S. Haltiwanger, S.S. Apte. 2007. O-fucosylation of thrombospondin type 1 repeats in ADAMTS-like-1/punctin-1 regulates secretion: Impications for the ADAMTS superfamily. J. Biol. Chem. 282: 17024-17031. PMID:17395588

S. Shi, C. Ge, Y. Luo, X Hou, R.S. Haltiwanger, P. Stanley. 2007. The threonine that carries fucose, but not fucose, is required for Cripto to facilitate Nodal signaling. J. Biol. Chem. 282: 20133-20141. PMID:17504756

A. Xu, N. Haines, M. Dlugosz, N.A. Rana, H. Takeuchi, R.S. Haltiwanger, K.D. Irvine. 2007. In vitro reconstitution of the modulation of Drosophila Notch-ligand binding by Fringe. J. Biol. Chem. 282: 35153-35162. PMID:17923477

Y. Luo, A. Nita-Lazar, R.S. Haltiwanger. 2006. Two distinct pathways for O-fucosylation of epidermal growth factor-like or thrombospondin type 1 repeats. J. Biol. Chem. 281: 9385-9392. PMID:16464858

Y. Luo, K. Koles, W. Vorndam, R.S. Haltiwanger, V.M. Panin. 2006. Protein O-fucosyltransferase 2 adds O-fucose to thrombospondin type 1 repeats. J. Biol. Chem. 281: 9393-9399. PMID:16464857

C. Loriol, F. Dupuy, R. Rampal, M.A. Dlugosz, R.S. Haltiwanger, A. Maftah, A. Germot. 2006. Molecular evolution of protein O-fucosyltransferase genes and splice variants. Glycobiology 16: 736-747. PMID:16679357

K. Kozma, J.J. Keusch, B. Hegemann, K.B. Luther, D. Klein, D. Hess, R.S. Haltiwanger, J. Hofsteenge. 2006. Identification and characterization of a β1,3-glucosyltransferase that synthesizes the Glc-β1,3-Fuc disaccharide on thrombospondin type 1 repeats. J. Biol. Chem. 281: 36742-36751. PMID:17032646

Y. Luo, R.S. Haltiwanger. 2005. O-fucosylation of Notch occurs in the endoplasmic reticulum. J. Biol. Chem. 280: 11289-11294. PMID:15653671

J.F. Arboleda-Velasquez, R. Rampal, E. Fung, D.C. Darland, M. Liu, M.C. Martinez, C.P. Donahue, M.F. Navarro-Gonzalez, P. Libby, P.A. D'Amore, M. Aikawa, R.S. Haltiwanger, K.S. Kosik. 2005. CADASIL mutations impair Notch3 glycosylation by Fringe. Hum. Mol. Genet. 14: 1631-1639. PMID:15857853

R. Rampal, J.F. Arboleda-Velasquez, A. Nita-Lazar, K.S. Kosik, R.S. Haltiwanger. 2005. Highly conserved O-fucose sites have distinct effects on Notch1 function. J. Biol. Chem. 280: 32133-32140. PMID:15994302

R. Rampal, A.S.Y. Li, M.J. Moloney, S.A. Georgiou, K.B. Luther, A. Nita-Lazar, R.S. Haltiwanger. 2005. Lunatic fringe, Manic fringe, and Radical fringe recognize similar specificity determinants in O-fucosylated EGF repeats. J. Biol. Chem. 280: 42454-42463. PMID:16221665

Book Chapters

RS Haltiwanger, L Wells, HH Freeze, P Stanley. 2017. Other Classes of Eukaryotic Glycans. In: Essentials of Glycobiology, Vol. 13. Cold Springs Harbor (NY).

To Top