The signalling profile of recombinant human orexin-2 receptor.

Orexin-A and orexin-B orchestrate their diverse central and peripheral effects via two G-protein coupled receptors, OX1R and OX2R, which activate multiple G-proteins. In many tissues, orexins activate extracellular signal-regulated kinase (ERK(1/2)) and p38 mitogen-activated protein kinase (MAPK); however, the mechanism by which OX2R alone mediates MAPK activation is not understood. This study describes the intracellular signalling pathways involved in OX2R-mediated ERK(1/2) and p38 MAPK activation. In HEK-293 cells stably over-expressing recombinant human OX2R, orexin-A/B resulted in a rapid, dose and time dependent increase in activation of ERK(1/2) and p38 MAPK, with maximal activation at 10 min for ERK(1/2) and 30 min for p38 MAPK. Using dominant-negative G-proteins and selective inhibitors of intracellular signalling cascades, we determined that orexin-A and orexin-B induced ERK(1/2) and p38 MAPK activation through multiple G-proteins and different intracellular signalling pathways. ERK(1/2) activation involves Gq/phospholipase C (PLC)/protein kinase C (PKC), Gs/adenylyl cyclase (AC)/cAMP/protein kinase A (PKA) and Gi cascades; however, the Gq/PLC/PKC pathway, as well as PKA is not required for OX2R-mediated p38 MAPK activation. Interestingly, orexin-B-induced ERK(1/2) activation is predominantly mediated through the Gq/PLC/PKC pathway. In conclusion, this is the first comprehensive signalling study of the human OX2R recombinant receptor, showing ERK(1/2) and p38 MAPK activation are regulated by differential signalling pathways in HEK-293 cells, and that the ERK(1/2) activation is severely affected by naturally occurring mutants associated with narcolepsy. Moreover, it is evident that the human OX2R has ligand specific effects, with orexin-B being more potent in this transfected system and this distinct modulation of the MAPKs through OX2R, may translate to the regulation of diverse biological actions of orexins.

Tang J ，Chen J ，Ramanjaneya M ，Punn A ，Conner AC ，Randeva HS ... -  《CELLULAR SIGNALLING》

Orexin-stimulated MAP kinase cascades are activated through multiple G-protein signalling pathways in human H295R adrenocortical cells: diverse roles for orexins A and B.

Ramanjaneya M ，Conner AC ，Chen J ，Kumar P ，Brown JE ，Jöhren O ，Lehnert H ，Stanfield PR ，Randeva HS ... -  《-》

Study of orexins signal transduction pathways in rat olfactory mucosa and in olfactory sensory neurons-derived cell line Odora: multiple orexin signalling pathways.

Gorojankina T ，Grébert D ，Salesse R ，Tanfin Z ，Caillol M ... -  《regulatory peptides》

A G protein-associated ERK pathway is involved in LPS-induced proliferation and a PTK-associated p38 MAPK pathway is involved in LPS-induced differentiation in resting B cells.

Kim J ，Yang HY ，Jang YS 《MOLECULAR IMMUNOLOGY》

Modulation of ERK 1/2 and p38 MAPK signaling pathways by ATP in osteoblasts: involvement of mechanical stress-activated calcium influx, PKC and Src activation.

Katz S ，Boland R ，Santillán G 《INTERNATIONAL JOURNAL OF BIOCHEMISTRY & CELL BIOLOGY》