The Prototoxin Lypd6B Modulates Heteromeric Î±3Î²4-Containing Nicotinic Acetylcholine Receptors But Not Î±7 Homomers
Prototoxins are a diverse family of membrane-tethered molecules expressed in the nervous system that modulate nicotinic cholinergic signaling, but their functions and specificity have yet to be completely explored. We tested the selectivity and efficacy of leukocyte antigen, PLAUR (plasminogen activator, urokinase receptor) domain-containing (LYPD)-6B on Î±3Î²4-, Î±3Î±5Î²4-, and Î±7-containing nicotinic acetylcholine receptors (nAChRs). To constrain stoichiometry, fusion proteins encoding concatemers of human Î±3, Î²4, and Î±5 (D and N variants) subunits were expressed in Xenopus laevis oocytes and testedwith or without LYPD6B. We used the 2-electrode voltage-clamp method to quantify responses to acetylcholine (ACh): agonist sensitivity (EC50), maximal agonist-induced current (Imax), and time constant (Ï„) of desensitization. For Î²4-Î±3-Î±3-Î²4-Î±3 and Î²4-Î±3-Î²4-Î±3-Î±3, LYPD6B decreased EC50 from 631 to 79 Î¼M, reduced Imax by at least 59%, and decreased Ï„. For Î²4-Î±3-Î±5D-Î²4-Î±3 and Î²4-Î±3-Î²4-Î±-Î±5D, LYPD6B decreased Imax by 63 and 32%, respectively. Thus, LYPD6B acted only on (Î±3)3(Î²4)2 and (Î±3)2(Î±5D)(Î²4)2 and did not affect the properties of (Î±3)2(Î²4)3, Î±7, or (Î±3)2(Î±5N) (Î²4)2 nAChRs. Therefore, LYPD6B acts as a mixed modulator that enhances the sensitivity of (Î±3)3(Î²4)2 nAChRs to ACh while reducing ACh-induced whole-cell currents. LYPD6B also negatively modulates Î±3Î²4 nAChRs that include the Î±5D common human variant, but not the Nvariant associated with nicotine dependence.
Digital Object Identifier (DOI)
Ochoa, Vanessa; George, Andrew A.; Nishi, Rae; and Whiteaker, Paul, "The Prototoxin Lypd6B Modulates Heteromeric Î±3Î²4-Containing Nicotinic Acetylcholine Receptors But Not Î±7 Homomers" (2016). Translational Neuroscience. 395.