title: Direct evidence of intracrine angiotensin II signaling in neurons.
abstract: The existence of a local renin-angiotensin system (RAS) in neurons was first postulated 40 years ago. Further studies indicated intraneuronal generation of ANG II. However, the function and signaling mechanisms of intraneuronal ANG II remained elusive. Since ANG II type 1 receptor (AT1R) is the major type of receptor mediating the effects of ANG II, we used intracellular microinjection and concurrent Ca(2+) and voltage imaging to examine the functionality of intracellular AT1R in neurons. We show that intracellular administration of ANG II produces a dose-dependent elevation of cytosolic Ca(2+) concentration ([Ca(2+)]i) in hypothalamic neurons that is sensitive to AT1R antagonism. Endolysosomal, but not Golgi apparatus, disruption prevents the effect of microinjected ANG II on [Ca(2+)]i. Additionally, the ANG II-induced Ca(2+) response is dependent on microautophagy and sensitive to inhibition of PLC or antagonism of inositol 1,4,5-trisphosphate receptors. Furthermore, intracellular application of ANG II produces AT1R-mediated depolarization of hypothalamic neurons, which is dependent on [Ca(2+)]i increase and on cation influx via transient receptor potential canonical channels. In summary, we provide evidence that intracellular ANG II activates endolysosomal AT1Rs in hypothalamic neurons. Our results point to the functionality of a novel intraneuronal angiotensinergic pathway, extending the current understanding of intracrine ANG II signaling.
authors.affiliation: Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania;
authors.forename: Elena
authors.initials: E
authors.lastname: Deliu
authors.forename: G Cristina
authors.initials: GC
authors.lastname: Brailoiu
authors.forename: Satoru
authors.initials: S
authors.lastname: Eguchi
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Hoffman
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Rabinowitz
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Tilley
authors.forename: Muniswamy
authors.initials: M
authors.lastname: Madesh
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Koch
authors.forename: Eugen
authors.initials: E
authors.lastname: Brailoiu
mesh_terms: D000804:Angiotensin II / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D047228:Angiotensin II Type 1 Receptor Blockers / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007031:Hypothalamus / Q000166:cytology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism; D008297:Male; D008845:Microinjections; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1 / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D053496:Inositol 1,4,5-Trisphosphate Receptors; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium
keywords: calcium; endoplasmic reticulum; renin-angiotensin system