The role of the C-terminal tail in protease-activated receptor-2-mediated Ca2+ signalling, proline-rich tyrosine kinase-2 activation, and mitogen-activated protein kinase activity.

C-terminal truncation mutants were made to investigate the role of the C-terminus in coupling proteinase-activated receptor-2 (PAR-2) to various signalling pathways. Membrane expression of the delta15, delta34, delta43, and delta34-43 mutants was similar; however, expression of deltatail was lost, as was agonist-mediated internalisation of deltatail, delta43, and delta34-43. Additionally, trypsin and SLIGKV-stimulated [3H]IP accumulation was abrogated in cells transiently expressing delta43 or delta34-43 truncations, but remained unaffected in cells expressing delta34 or delta15.

Proteinase-activated receptor-2-mediated activation of stress-activated protein kinases and inhibitory kappa B kinases in NCTC 2544 keratinocytes.

In this study we examined the regulation of the stress-activated protein (SAP) kinases and inhibitory kappa B kinases (IKKs) through stimulation of the novel G-protein-coupled receptor proteinase-activated receptor-2 in the human keratinocyte cell line NCTC2544. Trypsin and the peptide SLIGKV stimulated a time-dependent increase in both c-Jun N-terminal kinase and p38 mitogen-activated protein kinase activity. Trypsin also stimulated NF kappa B-DNA binding and the activation of the upstream kinases IKK alpha and -beta.

Proteinase-activated receptors.

Proteinase-activated receptors are a recently described, novel family of seven-transmembrane G-protein-coupled receptors. Rather then being stimulated through ligand receptor occupancy, activation is initiated by cleavage of the N terminus of the receptor by a serine protease resulting in the generation of a new tethered ligand that interacts with the receptor within extracellular loop-2. To date, four proteinase-activated receptors (PARs) have been identified, with distinct N-terminal cleavage sites and tethered ligand pharmacology.

QLS motif in transmembrane helix VII of the glucose transporter family interacts with the C-1 position of D-glucose and is involved in substrate selection at the exofacial binding site.

The liver-type (GLUT2) and brain-type (GLUT3) human facilitative glucose transporters exhibit distinct kinetics (Km values for deoxyglucose transport of approximately 11 mM and approximately 1.5 mM, respectively) and patterns of substrate transport (GLUT2 is capable of D-fructose transport, while GLUT3 is not). Using a range of chimeric glucose transporters comprised of regions of GLUT2 and GLUT3 studied by expression in Xenopus oocytes after microinjection of cRNA, we have proposed that the seventh putative transmembrane helix is intimately involved in the selection of transported substrate and that this region plays an important role in determining the Km for 2-deoxyglucose [Arbuckle, M.