Surface Chemistry, Biomaterials, Proteomics, Mechanisms of Cell Adhesion and Cell Migration, Cell Cycle Regulation, Enzymology at Membranes
B.Sc.(Hon) York University (1994); M.S. Univ. of Massachusetts (1996); Ph.D. University of Chicago (2001); Damon-Runyon Postdoctoral Fellow, Harvard Medical School (2001-2004); Burroughs-Wellcome Interface Career Award (2003-2007); 2009 National Science Foundation CAREER Award
The Yousaf Group will use a multidisciplinary approach that broadly interfaces surface chemistry and material science with biology to study fundamental questions in cell biology (ranging from Cell Migration to Cell Division) and to develop new tools applied to biotechnology (new types of microarrays).
The common theme in these programs is the development and utilization of new surface chemistries and materials to generate tools to investigate and probe important and complex biological systems. Each research program is problem driven and structured to address both fundamental and applied questions in material science and cell biology.
Students and Postdoctoral fellows in the group will be exposed and trained in a variety of areas ranging from organic synthesis, several analytical techniques, microfabrication, material science, microscopy, biochemistry and cell biology while pursuing these projects. The following are brief descriptions of the three main research programs that will be pursued:
Develop Tailored Microarrays Based on Self-Assembled Monolayers (SAMs) of Alkanethiolates on Gold to Discover and Study Small Molecule-Protein and Protein-Protein Interactions
The development of microarrays has revolutionized many areas of biological research and has also had a major impact in drug discovery programs. Microarrays combine the strengths of the immobilized assay format with the high-throughput capability of analyzing thousands of samples in parallel. Although there have been many recent advances in small molecule and protein microarray technology no system is able to quantitatively immobilize small molecules and proteins in defined densities and orientations onto a substrate that has very low non-specific binding (background) and be compatible with a variety of protein identification technologies. We will use a surface chemistry approach based on self assembled monolayers of alkanethiolates (SAMs) on gold, which are known to be the most flexible surfaces for studying bio-interfacial science, to develop tailored microarrays for a variety of biotechnological and cell biological applications. We will generate novel small molecule, protein and cDNA transfection microarrays that can be used for drug discovery, proteomic studies and to investigate signaling between molecular networks within a cell.
Chemical, Material and Cell Biological Approaches to Study Cell Division
To guard against developmental defects and devastating diseases such as cancer, all cells have evolved ways to exert tight control over the protein machinery that regulates the cell cycle. There are several mechanisms in place to control cell cycle progression, most notably transcriptional regulation and by two posttranslational modifications. One modification is phosphorylation reactions, which are catalyzed by cyclin-dependent kinases (CDK's) and several other protein kinases. The second is ubiquitination reactions, which are mediated by two multisubunit protein complexes, the Skp1-cullin-F-box-protein complex (SCF) and the anaphase-promoting complex/cyclosome (APC). Phosphorylation of proteins cause conformational changes that are well suited to reversibly alter the structural or catalytic properties of a protein, whereas polyubiquitination allows recognition and subsequent proteolytic destruction of the substrate proteins by the 26S proteosome (a multisubunit cellular factory that specializes in the unfolding and proteolysis of ubiquitin-tagged proteins). Ubiquitination of proteins therefore results in the complete inactivation of the modified protein, making this modification ideally suited to generate directionality in the cell cycle.
We will use a multidisciplinary strategy to study cell division, in particular, the role that proteolysis plays in late mitotic events and to develop novel materials to study how cell size and the cytoskeleton affect cell-cycle transitions, and to study the biochemistry of checkpoint proteins using FRET (fluorescence resonance energy transfer) and quantum dot strategies.
A Surface Chemistry and Materials Approach to Develop Model Substrates to Study PI(4,5)P2Lipid Raft Dependent Actin Polymerization
Membranes are a 2-dimensional floating world of complex short-lived associations. Locally differentiated patches of membrane - microdomains - are thought to form either spontaneously or through distinct signals, persist for a time and then disappear back into the disorder of the fluid mosaic. The organization of membranes into domains is biologically relevant because these domains can organize membrane functions, either by concentrating interacting molecules in particular regions of the surface or by excluding molecules and so preventing their interaction. In the past few years, receptors and signaling molecules have been shown to be concentrated in a particular class of membrane lipid domains termed 'lipid rafts'. Lipid rafts are small microdomains of lipids on the order of a few nanometers to a few microns that are non-equilibrium transient structures
found in both the plasma and endosomal membranes of eukaryotic cells. Lipid rafts appear to have many functions, although their complete roles are not well understood. Lipid rafts have been implicated in such diverse processes as polarized secretion, membrane transport, transcytosis across epithelial monolayers and the generation of cell polarity.
The importance of lipid rafts in signal transduction is highlighted by their enrichment of many signaling molecules such as receptor tyrosine kinases, mitogen-activated protein (MAP) kinases, adenylyl cyclase and lipid signaling intermediates. Certain lipid rafts provide entry sites for some intracellular bacteria and viruses and may promote budding of mature viruses (influenza, HIV) from infected cells. The actin cytoskeleton is also thought to be modulated by lipid rafts that contain the phospoinositide lipid PI(4,5)P2. This phosphoinositide accumulates at membrane rafts and promotes local co-recruitment and activation of specific signaling components at the cell membrane. Raft PI(4,5)P2 is further regulated by lipid kinases (eg. PI5), phosphatases (eg. synaptojanin) and raft-modulating proteins (eg. GAP43). Although there is some circumstantial evidence for the role of PI(4,5)P2 rafts in vesicle trafficking and actin cytoskeleton regulation, many questions remain unanswered due to a lack of spectroscopic tools and general model substrates to recapitulate lipid raft dependent events.
We will use a multidisciplinary approach to develop model systems that will address these important questions and to use this system as a platform to test lipid based drugs and to study enzymology at membranes.
Rapid In-Situ Generation of Two Patterned Chemoselective Orthogonal Surface Chemistries from a Single Hydroxy-Terminated Surface Using Controlled Microfluidic Oxidation. A. Pulsipher, N.P. Westcott, W. Luo, M.N. Yousaf. J. Am. Chem. Soc. 2009. 131, 7626-7632.
Electrochemical and Chemical Microfluidic Gold Etching to Generate Patterned and Gradient Substrates for Cell Adhesion and Cell Migration. N. P. Westcott, B. M. Lamb, M. N. Yousaf. Anal. Chem., 2009, 81, 3297�3303
Microfluidic Lithography of SAMs on Gold to Create Dynamic Surfaces for Directed Cell Migration and Contiguous Cell Co-Cultures. B.M. Lamb, D.G. Barrett, N.P. Westcott, M.N. Yousaf Langmuir 2008, 24, 8885�8889
Asymmetric Peptide Nanoarray Surfaces for Studies of Single Cell Polarization. D.K. Hoover, E.W.L. Chan and M.N. Yousaf. J. Am. Chem. Soc. 2008, 130, 3280-3281.
An Electroactive Catalytic Dynamic Substrate that Immobilizes and Releases Patterned Ligands, Proteins and Cells. Angew. Chem. Int. Ed. 2008, 47, 6267-6271.
A Photo-Electroactive Surface Strategy for Immobilizing Ligands in Patterns and Gradients for Studies of Cell Polarization. Mol. BioSyst. 2008, 4, 746-753
Electroactive nanoarrays for Biospecific Ligand Mediated Cell Adhesion. D.K. Hoover, E.J. Lee, E.WL. Chan and M.N. Yousaf. ChemBioChem 2007, 8, 1920-1923.
Combining Surface Chemistry with a FRET-Based Biosensor to Study the Dynamics of RhoA GTPase Activation in Cells on Patterned Substrates. L.Hodgson, E.W.L. Chan, K.M. Hahn and M.N. Yousaf. J. Am. Chem. Soc. 2007, 129, 9264-9265.
Rapid Patterning of Cells and Cell Co-Cultures with Spatial and Temporal Control on Surfaces through Centrifugation. D.G. Barrett and M.N. Yousaf. Angew. Chem. Int. Ed. 2007, 46, 7437-7439.
Surface-Chemistry Control to Silence Gene Expression in Drosophila Schneider 2 Cells through RNA Interference. E.W.L. Chan and M.N. Yousaf. Angew. Chem. Int. Ed. 2007, 46, 3881-3884.
Selective Immobilization of Ligands, Proteins and Cells to Electroactive Surfaces. E.W.L. Chan and M.N. Yousaf. J. Am. Chem. Soc. 2006, 128, 15542-15546.