عنوان

Cellular and molecular mechanisms underlying nicotine induced upregulation of alpha 7 nicotinic acetylcholine receptor expressed in xenopus oocytes: The role of CA2+ and CA2+-dependent signaling pathways

Number

TL48328

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Cellular and molecular mechanisms underlying nicotine induced upregulation of alpha 7 nicotinic acetylcholine receptor expressed in xenopus oocytes: The role of CA2+ and CA2+-dependent signaling pathways

General Material Designation

[Thesis]

First Statement of Responsibility

Mohammad Faridul Islam

Subsequent Statement of Responsibility

Farley, Joseph

Name of Publisher, Distributor, etc.

Indiana University

Date of Publication, Distribution, etc.

2015

Specific Material Designation and Extent of Item

212

Text of Note

Committee members: Hohmann, Andrea; Mackie, Ken; Rebec, George

Text of Note

Place of publication: United States, Ann Arbor; ISBN=978-1-321-89307-6

Dissertation or thesis details and type of degree

Ph.D.

Discipline of degree

Neuroscience

Body granting the degree

Indiana University

Text preceding or following the note

2015

Text of Note

Neuronal nicotinic-acetylcholine receptors (nAChRs) (e.g., α4β2, α7 Rs) appear to play critical roles in learning, memory, and various neuropathologies including nicotine addiction. Nicotine-upregulation of α7 Rs is thought to play a significant role in these phenomena. But whether nicotine-upregulation of α7 Rs in fact occurs, and the nature of its underlying mechanism(s), are largely unknown. Previous in vitro studies of α7 nAChRs heterologously expressed in Xenopus oocytes failed to observe nicotine-upregulation. These failures might have been due to incomplete removal of nicotine from the recording media, as a result of its intracellular accumulation and subsequent slow release from the oocytes, resulting in desensitization of α7 Rs during functional assays. Our GC/MS measurements confirmed that this was likely to be the case. In our experiments, 12-14 hr exposure to nicotine (100 µM), followed by extensive 7 hr washout yielded reliable, statistically-significant ~2-fold increases in macroscopic α7 R currents (as determined by two-electrode voltage clamp) and α7-protein (by Western blot). Less-extensive washout failed to produce upregulation; instead, desensitization was observed. Nicotine-upregulation was also correlated with the level of surface expression of α7 Rs, and did not involve new protein synthesis. Similar to nicotine, methyllycaconitine, a cell-permeable competitive antagonist of α7 Rs, as well as carbachol, a membrane-impermeable agonist, also produced upregulation, suggesting that ligand-binding to α7 Rs (but not activation of the receptors) was critical. Nicotine-upregulation of α7 Rs was unaffected by removal of extracellular Ca²⁺. However, intracellular Ca²⁺ chelation completely blocked upregulation. Several Ca²⁺ -dependent intracellular signaling pathways appeared to be critical for nicotine -upregulation: PP2B/calcineurin (inhibited by cyclosporine A), serine-threonine protein kinase-activity (inhibited by the compound H7), and perhaps one or more PKC isozymes (activated by a phorbol ester). In contrast, although protein tyrosine kinase (PTK) activity (inhibited by genistein) had a great influence on basal α7 currents [via positive allosteric modulatory (PAM-) and non-PAM effects], PTKs did not seem to participate in nicotine-produced upregulation. Tests of the potential contribution to nicotine-upregulation of cis-Golgi/ER quality control mechanisms (by the COPI-inhibitor CI-976) and α7-GPC signaling (via Gq/11; by a Substance-P analog) were inconclusive. These compounds strongly inhibited basal α7 currents.

Neurosciences; Physiology

Subject Term

Biological sciences;Alpha 7;Calcium;Nicotinic acetylcholine receptor;Upregulation

Gomes, Jorge Costa

Farley, Joseph

Subdivision

Neuroscience

Indiana University

Call Number

1706911511; 3712458

Electronic name

p

[Thesis]

276903

a

Y