title: Orexin/Hypocretin Signaling.
abstract: Orexin/hypocretin peptide (orexin-A and orexin-B) signaling is believed to take place via the two G-protein-coupled receptors (GPCRs), named OX1and OX2orexin receptors, as described in the previous chapters. Signaling of orexin peptides has been investigated in diverse endogenously orexin receptor-expressing cells - mainly neurons but also other types of cells - and in recombinant cells expressing the receptors in a heterologous manner. Findings in the different systems are partially convergent but also indicate cellular background-specific signaling. The general picture suggests an inherently high degree of diversity in orexin receptor signaling.In the current chapter, I present orexin signaling on the cellular and molecular levels. Discussion of the connection to (potential) physiological orexin responses is only brief since these are in focus of other chapters in this book. The same goes for the post-synaptic signaling mechanisms, which are dealt with in Burdakov: Postsynaptic actions of orexin. The current chapter is organized according to the tissue type, starting from the central nervous system. Finally, receptor signaling pathways are discussed across tissues, cell types, and even species.
authors.affiliation: Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, POB 66, FIN-00014, Helsinki, Finland. jyrki.kukkonen@helsinki.fi.
authors.forename: Jyrki P
authors.initials: JP
authors.lastname: Kukkonen
mesh_terms: D000818:Animals; D006801:Humans; D064446:Orexin Receptors / Q000378:metabolism; D000068797:Orexins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D064446:Orexin Receptors; D000068797:Orexins
keywords: Adenylyl cyclase; Calcium; Diacylglycerol lipase; Endocannabinoid; Gi; Gq; Gs; Heterotrimeric G-protein; Hypocretin; K+ channel; Na+/Ca2+-exchanger; Non-selective cation channel; OX1 receptor; OX2 receptor; Orexin; Phospholipase A2; Phospholipase C; Phospholipase D; Protein kinase C