Dr. Thomas Haas (on leave) BSc, PhD

The research interests of the lab focus on deciphering at an atomic level the mechanism by which intracellular signals are transformed into structural changes in the cell/extracellular matrix adhesion receptors (Integrins) that mediate homeostasis and pathological processes of thrombosis, inflammation and cancer.

Below are brief descriptions of the areas of active research.

Basic Research:

Nanotechnology: Over the past decade a number of laboratories have developed noninvasive cell-permeable peptide import techniques to deliver peptides and proteins into intact cells. The use of cell-permeable peptide import techniques to deliver peptides into intact cells is designed to overcome the barrier imposed by the cell membrane without compromising cell integrity. Their import into intact cells is dependent on a hydrophobic region selected from signal peptide sequences. Our laboratory has extended this import technique using amino-terminal coupled fatty acids as the hydrophobic anchor which not only allowed for the entry of peptides into intact cells, but also stabilized the structure of the cytoplasmic peptide. By varying the amino acid composition of the myristoylated aIIb cytoplasmic peptide the functional active of aIIbb3 integrin could be specifically up- or down-regulated integrin function. Research into defining the minimal structural epitopes that endow cell-permeability are underway for the future use of these molecular TAGs in scientific research and in drug development.

Mass Spectrometry (Protein Phosphorylation): Methods for examining the phosphorylation states of proteins and the specific sites of phosphorylation within proteins have been developed over the decade. These techniques typically involve running SDS gels, extracting bands from the gels followed by proteolytic digestion and analysis by a combination of microbore liquid chromatography, electrospray ionization tandem (MS/MS) ion trap mass spectrometry and negative ion mode precursor-ion scan of m/z 79 (PO-3). Recently, we have published a quantitative fentamole-sensitive method for identifying phosphorylated proteins and determining their site(s) of phosphorylation. This method does away with the use of radioactive isotopes. Further development of this methodology is integrated into our program.

Mass Spectrometry (Protein Interactions): Our laboratory has used mass spectrometry as a method to study and characterize the formation of a noncovalent peptide-peptide and peptide-metal ion complexes. These studies have involved both the extracellular ligand binding pocket of integrins and their cytoplasmic domain. Refinement of mass spectrometry parameters and sample/solvent conditions are required in order for these techniques to become common methodology.

Applied Research:

Integrin Biology: Cell-cell and cell-substratum interactions are central to vascular cell adhesion, migration, growth and differentiation, and extracellular matrix assembly. These basic biological events determine processes of development, homeostasis and thrombosis, inflammation, and tumor invasion and metastasis. These cellular interactions are mediated through cell-surface proteins belonging to the integrin family of cell adhesion receptors. The interactions between integrins and their ligands are central to many of these physiological and pathological processes. Integrin-ligand interactions are tightly regulated through a process involving their cytoplasmic tails and by divalent metal ions. The $3 integrin family is the primary focus of this group due to their clinical relevance in cardiovascular diseases and cancer.

• Haas, T.A., Plow, E.F.: The cytoplasmic domain of aIIbb3. A ternary complex of the integrin a and b subunits and a divalent cation. J.Biol.Chem. 271:6017-6026, 1996.
• Haas, T.A., Plow, E.F.: Development of a structural model of the cytoplasmic domain of an integrin. Protein Engineering 10:1395-1405, 1997.
• Huang, W., Haas, T.A., Biesterfeldt, J., Mankawsky, L., Koo, A., Blanton, R., Lee, X.: Purification and crystallization of a novel membrane anchored protein: the Schistosoma haematobium serpin. Acta Crystallographica D55:350-352, 1999.
• Haas, T.A., Vinogradova, O., Plow, E.F., Qin, J.: A structural basis for integrin activation by the cytoplasmic tail of the aIIb subunit. Proc.Natl,Acad.Sci. 97:1450-1455, 2000
• Plow, E.F., Haas, T.A., Zhang, L., Loftus, J., Smith, J.W.: Ligand binding to integrins. J.Biol.Chem. 275:21785-21788, 2000.
• Plow, E.F., Cierniewski, C.S., Xiao, Z. Haas, T.A.: aIIbb3 and its antagonism at the new millennium. Thromb. Haemost. 86:34-40, 2001.
• Ruse, C.I., Kinter,M., Willard, B., Jin, J.P., Haas, T.A., Bond, M.: Quantitative dynamics of site-specific protein phosphorylation determined using liquid chromatography electrospray ionization mass spectrometry. Anal.Chem. 74: 1658-1664, 2002
• Cierniewska-Cieslak, C., Cierniewski, C., Blecka, K., Papierak, M., Zhang, L., Haas, T.A., Plow, E.F.: Identification and characterization of two cation binding sites in the b3 integrin subunit. J.Biol.Chem. 277:11126-11134, 2002.
• Gudz, T.I., Schneider, T.E., Haas, T.A., Macklin, W.B.: Myelin proteolipid protein forms a complex with integrins and may participate in integrin receptor signaling in oligodendrocytes. J. Neurosci. 22:7398-407,2002.
• Vinogradova, O., Velyviene, A., Velyvis, A., Hu, B., Haas, T.A., Plow, E., Qin J.: A structural mechanism of integrin aIIbb3 "inside-out" activation as regulated by its cytoplasmic face. Cell 110:587-597, 2002.
• Xiong, Y.-M., Haas, T.A., Zhang, L: Identification of functional segments within the b2 I-domain of integrin aMb2. J.Biol.Chem. 277: 46639 - 46644, 2002.
• Ugarova, T.P., Lishko, V.K., Merulov, S.M., Yakubenko, V.P., Ryabokon, P.P., Yee, V.C., Haas, T.A.: Sequence _377-395 (P2), but not _190-202 (P1), is the binding site for the aM I-domain of integrin aMb2 in the C-domain of fibrinogen. Biochemistry, 42:9365-73, 2003.
• Vinogradova, O., Vaynberg, J., Kong, X., Haas, T.A., Plow, E.F., Qin, J.  Membrane-mediated structural transitions at the cytoplasmic face during integrin activation. PNAS101: 4094-4099, 2004.
• Stefano, G., Renna, L., Chatre, L., Hanton, S., Haas, T.A., Brandizzi, F.: ARF3 plays a role in the binding of a GRIP domain of a peripheral matrix protein to the Golgi apparatus in plant cells. Plant J., 2006
• Das U, Selvakumar P, Sharma RK, Haas TA, Dimmock JR.  N-acyl-3,5-bis(arylidene)-4-piperidones and related compounds which stimulate fyn kinase.  J Enzyme Inhib Med Chem. 2007 Aug;22(4):451-5.
• Haas, T.A.  Allosteric regulation of αIIbβ3 by β3 95-105  (2008) Thrombosis and Haemostasis, 99 (4), pp. 701-710.
• Haas, T.A., Taherian, A., Berry, T., Ma, X. Identification of residues of functional importance within the central turn motifs present in the cytoplasmic tails of integrin αIIb and αV subunits (2008) Thrombosis Research, 122 (4), pp. 507-516.
• Haas, T.A.  Discrete functional motifs reside within the cytoplasmic tail of αV integrin subunit (2008) Thrombosis and Haemostasis, 99 (1), pp. 96-107.
• Haas TA. vAllosteric regulation of alpha(IIb)beta(3) by beta(3) 95-105.  Thromb Haemost. 2008 Apr;99(4):701-10.
• Taherian A, Li X, Liu Y, Haas TA.  Differences in integrin expression and signaling within human breast cancer cells.  BMC Cancer. 2011 Jul 13;11:293.
• Li X, Liu Y, Haas TA. Skelemin in integrin α(IIb)β(3) mediated cell spreading.  Biochemistry. 2013 Jan 29;52(4):681-9.
• Li X, Liu Y, Haas TA.  Peptides derived from central turn motifs within integrin αIIb and αV cytoplasmic tails inhibit integrin activation.  Peptides. 2014 Dec;62:38-48