RESUMO
One of the histopathological features of Alzheimer's disease (AD) is higher order neurofibrillary tangles formed by abnormally aggregated tau protein. The sequence 275VQIINK280 in the microtubule-binding domain of tau plays a key role in tau aggregation. Therefore, an aggregation inhibitor targeting the VQIINK region in tau may be an effective therapeutic agent for AD. We have previously shown that the Fab domain (Fab2r3) of a tau antibody that recognizes the VQIINK sequence can inhibit tau aggregation, and we have determined the tertiary structure of the Fab2r3-VQIINK complex. In this report, we determined the tertiary structure of apo Fab2r3 and analyzed differences in the structures of apo Fab2r3 and Fab2r3-VQIINK to examine the ligand recognition mechanism of Fab2r3. In comparison with the Fab2r3-VQIINK structure, there were large differences in the arrangement of the constant and variable domains in apo Fab2r3. Remarkable structural changes were especially observed in the H3 and L3 loop regions of the complementarity determining regions (CDRs) in apo Fab2r3 and the Fab2r3-VQIINK complex. These structural differences in CDRs suggest that formation of hydrophobic pockets suitable for the antigen is important for antigen recognition by tau antibodies.
Assuntos
Doença de Alzheimer/metabolismo , Motivos de Aminoácidos , Anticorpos Monoclonais/metabolismo , Agregados Proteicos , Agregação Patológica de Proteínas/metabolismo , Proteínas tau/metabolismo , Sequência de Aminoácidos , Anticorpos Monoclonais/química , Regiões Determinantes de Complementaridade/química , Regiões Determinantes de Complementaridade/metabolismo , Cristalografia por Raios X , Humanos , Fragmentos Fab das Imunoglobulinas/química , Fragmentos Fab das Imunoglobulinas/metabolismo , Modelos Moleculares , Emaranhados Neurofibrilares/química , Emaranhados Neurofibrilares/metabolismo , Ligação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Proteínas tau/química , Proteínas tau/imunologiaRESUMO
Neurofibrillary tangles formed by abnormally aggregated tau protein are a histopathological feature of tauopathies. A tau aggregation inhibitor is a potential therapeutic agent for tauopathies. In this study, we prepared a monoclonal antibody for tau, monoclonal antibody to tau protein (Tau2r3), using as epitope the 272 GGKVQIINKKLD283 peptide in the microtubule-binding domain of tau, the key region mediating tau aggregation. We show that Tau2r3 clearly inhibits tau aggregation. To analyze the inhibition mechanism of Tau2r3, we solved the crystal structure of the Fab domain of Tau2r3 (Fab2r3) in complex with the VQIINK peptide. In the Fab2r3-VQIINK structure, the second and sixth polar residues and the fourth hydrophobic residue of VQIINK are crucial for binding to Fab2r3. The structural data for the Fab2r3-VQIINK complex could contribute to the design of new tau aggregation inhibitors.
