Conformational Changes in the Lower Palm Domain of ASIC1a Contribute to Desensitization and RFamide Modulation

Erin N Frey,Clem John Wegman,Chenglong Li,Candice C Askwith,Ryan E Pavlovicz,Stuart E Dryer

doi:10.1371/journal.pone.0071733

Erin N Frey, Clem John Wegman + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0071733

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Abstract

Acid-sensing ion channel 1a (ASIC1a) is a proton-gated cation channel that contributes to fear and pain as well as neuronal damage following persistent cerebral acidosis. Neuropeptides can affect acid-induced neuronal injury by altering ASIC1a inactivation and/or steady-state desensitization. Yet, exactly how ASIC1a inactivation and desensitization occur or are modulated by peptides is not completely understood. We found that regions of the extracellular palm domain and the β11-12 linker are important for inactivation and steady-state desensitization of ASIC1a. The single amino acid substitutions L280C and L415C dramatically enhanced the rate of inactivation and altered the pH-dependence of steady-state desensitization. Further, the use of methanethiosulfonate (MTS) reagents suggests that the lower palm region (L280C) undergoes a conformational change when ASIC1a transitions from closed to desensitized. We determined that L280C also displays an altered response to the RFamide peptide, FRRFamide. Further, the presence of FRRFamide limited MTS modification of L280C. Together, these results indicate a potential role of the lower palm domain in peptide modulation and suggest RFamide-related peptides promote conformational changes within this region. These data provide empirical support for the idea that L280, and likely this region of the central vestibule, is intimately involved in channel inactivation and desensitization.

Highlights

ASICs are proton-gated, voltage-insensitive cation channels expressed throughout the nervous system [1,2,3,4]
These results suggested that L280 and L415 play a role in channel inactivation
Mutations L280C, I307C, and L415C maintain the basic mechanisms of ASIC activity, the characteristics of the channels are slightly perturbed

Summary

Introduction

ASICs are proton-gated, voltage-insensitive cation channels expressed throughout the nervous system [1,2,3,4]. ASIC1a causes neuronal death following prolonged extracellular acidosis within the central nervous system [12,13]. Acidosis and ASIC1a-mediated neuronal dysfunction have been implicated in stroke, multiple sclerosis, and amyotropic lateral sclerosis [12,14,15,16]. Acidosis-mediated neuronal death is limited by induction of steady-state desensitization in ASIC1a [17]. Steady-state desensitization occurs during slow or incremental changes in pH that are not sufficient to provoke robust activation of the channel [18]. Steady-state desensitization and inactivation are often intertwined [19,20,21]. Inactivation has been implicated in both sustained acid-dependent responses (pain) and ASIC’s role in behavior [22,23]

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