Dorothy and Patrick E. Gorman chair of biological ultrastructure
Antibodies that recognize crystal surfaces (L. Addadi)
Mechanism of cell adhesion using crystal substrates (L. Addadi, in collaboration with B. Geiger)
Protein-Crystal Interactions; BiomineralizationBiomineralization encompasses all mineral-containing tissues formed by organisms to fulfill a variety of different functions, such as in shells,skeleton, teeth and the like. Crystal formation is often controlled in all its aspects, from their incept to their orientation, size, shape and assembly. Control is exercized through specialized proteins that recognizespecific crystal surfaces during the growth of the crystals. Recognition is based on molecular complementarity between the protein and the crystal structure on defined planes. The understanding of these processes is also relevant to research on advanced materials. Biology provides an insight into unconventional strategies of a degree of sophystication yet unconceived in man-made materials. (with S. Weiner)
Crystals are also involved in many pathological conditions: some
types of arthritis, atherosclerosis and kidney stones are common examples.
The organism, exposed to the crystals, reacts with its defence system,
the immune system, producing specific antibodies. Antibodies that interact
specifically with surfaces such as those of cholesterol crystals were
thus produced, selected and investigated. These same antibodies recognize
cholesterol in organized domains also under the form monolayers at the
air-water interface and in cell membranes. Molecular recognition is
based on complementarity between the antibody binding site and defined
crystal surface features. Understanding the rules of these interactions
is of fundamental, as well as potentially applicative interest.
Cell adhesion is a very complex and important, yet not sufficiently understood phenomenon, involving a battery of components inside and outside the cell. One basic question concerns what does a living cell 'feel' or 'see' when it approaches an extracellular surface. Using crystals as substrates for adhesion, we find that even cells have the highest level of recognition for the surfaces to which they do (or do not) adhere. These investigations provide an insight into some basic aspects of the molecular mechanism of adhesion. They may also be relevant to various physiological and pathological situations, of which osteoclast-crystal interactions in bone resorption is only an example. (with B. Geiger)