Molecular recognition studies at interfaces of antibodies with structured domains

Lia Addadi Antibodies are the tools that vertebrates evolved to recognize foreign invaders. They do so by virtue of complementarity of their binding sites to the surface of their target, the antigens. Julia Mahamid Our laboratory studies antibodies that recognize ordered molecular self-assemblies. Noa Rubin The basic concept is that the immune system should relate to molecular self-assemblies such as crystals, organized fibers or 2D arrays of molecules, in the same manner as to any other invader. Surfaces of organized molecular arrays have characteristics akin to those Luana Scheffer of a macromolecular surface. The establishment of high affinity interactions between the antibody and the self-assembled structure implies in this case the recognition of a repetitive series of molecular moieties in the correct arrangement. The molecular recognition of structural antibodies to organized arrays has potential relevance to research on cholesterol-rich domains [1] and amyloids [4], as well as to pathological crystallization diseases, such as [3] and [2].

[1] Cholesterol-rich domains (Luana Scheffer, in collaboration with Prof. Anthony H. Futerman, Dept of Biological Chemistry) A significant advance in the understanding of membrane organization, function and structure developed with the suggestion that plasma membranes of animal cells contain laterally segregated domains, the so-called ‘lipid rafts’, formed by dynamical clustering of cholesterol and sphingolipids in organized structures. The structure and composition of these submicron domains is still under investigation. In order to glean structural knowledge about this type of domains, a monoclonal antibody (405F) was raised and selected against a crystalline 60% cholesterol/40% ceramide mixed monolayer, whose molecular organization was determined. The antibody interacts specifically with the mixed cholesterol-ceramide monolayers, but not with pure monolayers of cholesterol or ceramide. Immunofluorescence experiments performed on cultured COS cells with antibody 405F directly visualized cellular microdomains sensitive to the modulation of the intracellular levels of ceramide and cholesterol. Since the antibody interacts with ordered arrays of cholesterol-ceramide, the labeling may indicate the existence of these domains in the cell [2] Atherosclerosis (Noa Rubin, in collaboration with Dr. Howard Kruth, NIH, Bethesda) In this disease, deposits of cholesterol ester, cholesterol monohydrate crystals, cellular Department of waste products and calcium build up in the inner lining of arteries, forming plaques that Structural Biology prevent blood flow, causing heart disease. We raised and selected antibodies that specifically interact with cholesterol monohydrate crystals. Histology sections of aortas from atherosclerotic mice are immuno-labeled by these antibodies (36A1 and 58B1), while an irrelevant antibody (48E) does not interact 972 8 934 2228 with the crystals in the sections. Antibody 58B1 labeling is highly selective to the lesion plaque and to the monohydrate crystals whereas antibody 36A1 labels, in addition to plaque crystals, also other regions. 972 8 934 4136 [3] Gout (Julia Mahamid, in collaboration with Prof. Dan Caspi, Sourasky Medical Center, Tel Aviv) Gout is an inflammatory joint disease triggered by the deposition of elongated plate- [email protected] like crystals of monosodium urate monohydrate (MSUM) within joints. Although urate ion supersaturation is a pre-requisite for crystal deposition, it is not sufficient for the formation of pathological crystals. Antibodies elicited against crystals are chemically and www.weizmann.ac.il/sb/faculty_pages/ Addadi structurally complementary to the crystal surface they recognize. It is thus conceivable that such antibodies may accelerate crystal formation by stabilizing the crystal nuclei

Life Science Open Day | 2006 | Weizmann Institute of Science Fig. 1 (A) Schematic representation of the possible complementarity between antibody variable regions (a, b, c, d) and organized crystal surfaces. (B) Docking model of monoclonal antibody 36A1 (raised and selected against cholesterol monohydrate crystals) onto the (301) face of the cholesterol monohydrate crystal. and reducing the activation energy required for the nucleation membrane cholesterol microdomains responsive to cholesterol process. We have examined the nucleating effect of antibodies trafficking. J. Lipid Res., 42(9), 1492-500. (IgG and IgM) isolated from 13 gout patients, 3 rheumatoid arthritis patients, 3 patients, 2 psoriatic arthritis Acknowledgements patients and 5 healthy individuals. We conclude that gouty Prof. Lia Addadi is incumbent of the Dorothy and Patrick Gorman individuals develop a population of anti-MSUM antibodies, which professorial chair of Biological Ultrastructure, and L.S. is the have a nucleating effect on MSUM in new crystallizations. These recipient of the Eshkol Fellowship, administered by the Israel findings may explain the common pathogenesis of recurrent Ministry of Science. This work was supported by a grant from attacks observed in gout. the Israel Science Foundation, administered by the Israel Academy of Sciences and by a Weizmann Institute of Science [4] Amyloids (Noa Rubin) –Tel Aviv Sourasky Medical Center Collaborative Grant in Amyloids are a large family of misfolded proteins related Biomedical Research. This work was supported by the Helen to many fatal diseases such as Alzheimer, Parkinson, Prions & Milton A.Kimmelman Center for Biomolecular Structure & and others. A possibility that is emerging is that the amyloid Assembly. fiber structure may be a stable structure for most, if not all, polypeptides, irrespective of their sequence, provided the appropriate conditions exist. No single defined structure has been determined to be common to all amyloid protofilaments, although the cross-β conformation is the common secondary structure denominator in amyloid. Different pathological and artificial amyloids have different morphologies at the fiber level. We are investigating the relation between fiber morphology and amyloid molecular structure. To this end, we intend to study the interaction of conformational monoclonal antibodies with amyloid fibers. The antibodies are raised and selected to recognize the amyloid form, but not the native form of the peptides.

Selected publications Scheffer, L., Solomonov, I., Weygand, M.J., Kjaer, K., Leiserowitz, L., and Addadi, L.(2005) Structure of cholesterol/ceramide monolayer mixtures: implications to the molecular organization of lipid rafts. Biophys J.,88(5),3381-91. Geva, M., Eisenstein, M., and Addadi, L. (2004) Antibody recognition of chiral surfaces. Structural models of antibody complexes with leucine-leucine-tyrosine crystal surfaces. Proteins, 55(4), 862-73 Addadi, L., Geva, M., and Kruth, H.S. (2003) Structural information about organized cholesterol domains from specific antibody recognition. Biochim Biophys Acta, 1610(2),208-16. Review. Kruth, H.S., Ifrim, I., Chang, J., Addadi, L., Perl-Treves, D., and Zhang, W.Y. (2001) Monoclonal antibody detection of plasma