Synthesis of isoprenoid chain-contained chemical probes for an investigation of molecular interactions by using quartz crystal microbalance

S-Geranylgeranyl-L-glutathione is a ligand for human B cell-confinement receptor P2RY8

Germinal centres are important sites for antibody diversification and affinity maturation, and are also a common origin of B cell malignancies. Despite being made up of motile cells, germinal centres are tightly confined within B cell follicles. The cues that promote this confinement are incompletely understood. P2RY8 is a Gα13-coupled receptor that mediates the inhibition of migration and regulates the growth of B cells in lymphoid tissues1,2. P2RY8 is frequently mutated in germinal-centre B cell-like diffuse large B cell lymphoma (GCB-DLBCL) and Burkitt lymphoma1,3-6, and the ligand for this receptor has not yet been identified. Here we perform a search for P2RY8 ligands and find P2RY8 bioactivity in bile and in culture supernatants of several mouse and human cell lines. Using a seven-step biochemical fractionation procedure and a drop-out mass spectrometry approach, we show that a previously undescribed biomolecule, S-geranylgeranyl-L-glutathione (GGG), is a potent P2RY8 ligand that is detectable in lymphoid tissues at the nanomolar level. GGG inhibited the chemokine-mediated migration of human germinal-centre B cells and T follicular helper cells, and antagonized the induction of phosphorylated AKT in germinal-centre B cells. We also found that the enzyme gamma-glutamyltransferase-5 (GGT5), which was highly expressed by follicular dendritic cells, metabolized GGG to a form that did not activate the receptor. Overexpression of GGT5 disrupted the ability of P2RY8 to promote B cell confinement to germinal centres, which indicates that GGT5 establishes a GGG gradient in lymphoid tissues. This work defines GGG as an intercellular signalling molecule that is involved in organizing and controlling germinal-centre responses. As the P2RY8 locus is modified in several other types of cancer in addition to GCB-DLBCL and Burkitt lymphoma, we speculate that GGG might have organizing and growth-regulatory roles in multiple human tissues.

Exploring the interactions between isoprenoid chain and labdenediol diphosphate synthase based on molecular docking and quartz crystal microbalance

Many natural products and biosynthetic intermediates contain isoprenoid chains. Isoprenoid chains are believed to interact with some proteins in the biological systems, but such interactions remain poorly understood. Here labdenediol diphosphate synthase (LPPS) was used as a model to explore the molecular interactions involving isoprenoid chains. Both homology modeling and docking simulation results indicated that binding form between isoprenoid chain and LPPS is dominated by hydrophobic forces in one binding site. The interactions were also examined via quartz crystal microbalance (QCM) technology using synthetic isoprenoid chain-contained probes. The binding constant (1.51 μM(-1)), binding site number (n = 1) and key amino acid residues (Y196, F262, W266, F301, F308, W398, W439, and Y445) were obtained. Both computational and QCM results suggested that LPPS interacts strongly with farnesyl and geranylgeranyl groups. These interactions are primarily caused by hydrophobic and π-π interaction nature. Together, this study provided insightful information to understand molecular interactions between isoprenoid chains and proteins.