The latest progress of chemical array techniques for chemical biology research○Akiko Saito,1 Yasumitsu Kondoh,1 Sumihiro Maeda,2 Kayoko Kawai,1 Tatsuhiko Sudo,1Akihiko Takashima,2 Hiroyuki Osada1
1Chemical Biology Department, RIKEN Advanced Science Institute,
2Laboratory for Alzheimer's Disease RIKEN Brain Science Institute, RIKEN
Chemical biology elucidating biological systems with small molecules (as chemicaltools), attracts attention of organic chemists and molecular biologists now. Small-molecules
which specifically modulate the function of proteins of interest, so called bioprobes, arepowerful tools for chemical biology. The high throughput screening system to identify theaimed inhibitors and bioprobes is very important. Chemical array platform is a promising
approach to detect ligand molecules for individual proteins. We have developed aphotoaffinity chemical array to immobilize structurally diverse small-molecules, naturalproducts, its derivatives and drugs on a solid support in a functional group independentmanner. The advantages of photoaffinity cross-linking method are to immobilize a variety ofcompounds on a single chip easily and to expose the diverse moieties of small molecule
toward a protein of interest on a chip. In addition, we have developed photoaffinity SPR
imaging platform to observe multiple interactions between non-labeled proteins andsurface-bound small-molecules. In this symposium, we report the recent results of chemical
biology studies with chemical array and the remaining issues for chemical array.
Tau proteins are microtubule-associated proteins and known to be related with
Alzheimer's disease. Tau proteins are abundant in neurons of the central nervous system andare less elsewhere. The aggregation of tau protein is often found in the Alzheimer's disease
brain and is thought to contributeto neuronal dysfunction. There is apossibility that the inhibitor of thetau protein aggregation become apotent preventer of Alzheimer'sdisease. In order to discoversmall-molecules inhibiting the tau
aggregation, we screened 2011
compounds by tau protein binding
assay using chemical array. As
tau-binding
compounds,
202
compounds were identified bychemical array assay. Among them,
53 compounds were confirmed tobind to tau protein directly by ourphotoaffinity SPR binding assay. Finally, it was revealed that 42 compounds have inhibitory
activity for tau aggregation.
p38 mitogen-activated protein kinase (MAPK) has been identified as anti-inflammatory
drug binding protein, a lipopolysaccharide-activated protein kinase, or a stress-responsive
protein kinase. We have studied to elucidate the precise molecular mechanism by which p38
can exert various responses to stimuli, and we previously showed that p62/SQSTM1 bound toregulate p38 in vivo. Our biological studies revealed that two domains of p62 play an essential
role for the interaction with p38, however it was not clear whether both domains interactedwith p38 directly. So we attempt to use the photoaffinity SPR imaging platform to determine
the binding site of p62/SQSTM1 to p38. SPR imaging experiments using photoaffinity linker
to immobilize the peptides derived from p62 on gold substrate indicated that the domain
comprising amino acids 164-190 of p62 binds to p38 directly. These SPR analysis data andempirical biologic data revealed that the binding site of p62 to p38 is the domain
corresponding to 173-182.
References
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A. Saito, K. Kawai, H. Takayama, T. Sudo and H. Osada. Chem. Asian J. 2008, 3,1607-1612.

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K. Kawai, A. Saito, T. Sudo and H. Osada, J. Biochem. 2008, 143, 765-772.