title: Differential targeting and function of alpha2A and alpha2C adrenergic receptor subtypes in cultured sympathetic neurons.
abstract: Previous research suggested that alpha2A and alpha2C adrenergic receptor (AR) subtypes have overlapping but unique physiological roles in neuronal signaling; however, the basis for these dissimilarities is not completely known. To better understand the observed functional differences between these autoreceptors, we investigated targeting and signaling of endogenously expressed alpha2A and alpha2CARs in cultured sympathetic ganglion neurons (SGN). At Days 1 and 4, alpha2A and alpha2CARs could be readily detected in SGN from wild-type mice. By Day 8, alpha2A ARs were targeted to cell body, as well as axonal and dendritic sites, whereas alpha2C ARs were primarily localized to an intracellular vesicular pool within the cell body and proximal dendritic projections. Expression of synaptic vesicle marker protein SV2 did not differ at Day 8 nor co-localize with either subtype. By Day 16, however, alpha2C ARs had relocated to somatodendritic and axonal sites and, unlike alpha2A ARs, co-localized with SV2 at synaptic contact sites. Consistent with a functional role for alpha2 ARs, we also observed that dexmedetomidine stimulation of cultured SGN more efficiently inhibited depolarization-induced calcium entry into older, compared to younger, cultures. These results provide direct evidence of distinct developmental patterns of endogenous alpha2A and alpha2C AR targeting and function in a native cell system and that maturation of SGN in culture leads to alterations in neuronal properties required for proper targeting. More importantly, the co-localization at Day 16 of alpha2C ARs at sites of synaptic contact may partially explain the differential modulation of neurotransmitter release and responsiveness to action potential frequency observed between alpha2A and alpha2C ARs in SGN.
authors.affiliation: Laboratório de Fisiologia do Exercício, Escola de Educação Física e Esporte, Universidade de Sao Paulo, Av. Prof. Mello Moraes 65, 05508-900 Sao Paulo, SP, Brazil.
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Brum
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University Medical School, 157 Beckman Center, 279 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Carl M
authors.initials: CM
authors.lastname: Hurt
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University Medical School, 157 Beckman Center, 279 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Olga G
authors.initials: OG
authors.lastname: Shcherbakova
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University Medical School, 157 Beckman Center, 279 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Kobilka
authors.affiliation: Department of Anesthesia, Stanford University Medical School, Stanford, CA 94305, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Angelotti
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D016257:Fura-2; D007150:Immunohistochemistry / Q000379:methods; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000502:physiology*; D018341:Receptors, Adrenergic, alpha-2 / Q000172:deficiency / Q000502:physiology*; D017783:Superior Cervical Ganglion / Q000166:cytology*; D013997:Time Factors
chemical_list: C547769:Adra2a protein, mouse; C547775:Adra2c protein, mouse; D008562:Membrane Glycoproteins; D008869:Microtubule-Associated Proteins; C079240:Mtap2 protein, mouse; D009419:Nerve Tissue Proteins; D018341:Receptors, Adrenergic, alpha-2; C489614:Sv2a protein, mouse; D004299:Dopamine beta-Hydroxylase; D002118:Calcium; D016257:Fura-2