Program Summary
This Maximizing Investigators’ Research Award (MIRA) proposal is directly relevant to the long-range
plans of the National Institute of General Medical Sciences (NIGMS). Our laboratory received continuous
NIGMS funding since 2004 that allowed us to make substantial advances in our understanding of the
mechanisms of the dynamic contacts between neighboring cells (adherens junctions), as well as between
cells and the extracellular matrix (focal adhesions structures). These cell junctions, in addition of holding
animal cells together, communicate signals and control the stress placed upon cells.
Over the past 16 years, we contributed important mechanistic discoveries towards an understanding of
· how the cell-cell junctions connect cells in tissues to regulate tissue homeostasis that are crucial to
provide the tissue barrier of epithelia, as well as cell migration and proliferation; and
· how cell junctions initiate and maintain cell adhesion while regulating the organization of the underlying
actin cytoskeleton by establishing a center for cell signaling and gene transcript regulation.
Such processes are highly dynamic and tightly regulated. Our laboratory focused on defining the activation
mechanisms of key regulators of these cell junctions that we studied biochemically and in live cells. Our
discoveries were accelerated by our development of new techniques that overcame significant structural
biology hurdles that stalled the field and that are applicable to many other structural biology studies.
We discovered how talin activates vinculin, two ubiquitously expressed, actin-binding proteins, to stabilizes
focal adhesions and thereby suppressing cell migration. Our high-resolution vinculin crystal structures, that
we confirmed biochemically and in live cells, showed the auto-inhibitory intramolecular interactions that
inactivate vinculin and thereby prevent vinculin from binding to the actin cytoskeleton.
On the other hand, our high-resolution crystal structures of a-catenin, a crucial mediator of intercellular
adhesions, revealed the mechanistic roles that its quaternary structures play in cell-cell adhesion and in
the formation of the dynamic link to the actin cytoskeleton. Significantly, our discoveries led to mechano-
transduction studies of cell-cell and cell-matrix junctions on how cells sense and transmit forces.
More recently, we discovered how lipid binding to vinculin, to its cardiac isoform metavinculin, and to talin
regulates focal adhesion turnover. This knowledge and expertise are the foundation for further discoveries
that will additionally focus on the understudied role that the plasma membrane plays in cell adhesion.
In the long run, we hope to gain a complete understanding of cell adhesion by attaining a near atomic
structure of a “synthetic” cell junction. The regulation and dysregulation of cell junctions are fundamental to
many biological processes such as development and cancer, and our proposed studies have therefore
both basic and potentially translational significance.