Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 16 de 16
Filter
1.
Dermatol Surg ; 48(2): 232-238, 2022 Feb 01.
Article in English | MEDLINE | ID: mdl-34923536

ABSTRACT

BACKGROUND: Pain assessment plays an important role in dermatologic surgery. The numeric rating scale (NRS), visual analog scale (VAS), verbal rating scale (VRS), and Faces Pain Scale (FPS) are commonly used scales for pain measurement. Conflicting evidence exists regarding the use of each. Prompt pain recognition and treatment during procedures result in higher patient satisfaction. OBJECTIVE: Determine the most applicable scale for acute pain measurement in dermatologic surgery. MATERIALS AND METHODS: This systematic review was performed in accordance with PRISMA-Supplemental Digital Content 4, http://links.lww.com/DSS/A976 (PROSPERO; CRD42018091058). PubMed, Cochrane, EMBASE, Scopus, and Web of Science were searched between April 24, 2018, and May 06, 2018. The search query consisted of pain, pain measurement (NRS, VAS, VRS, and FPS), and assessment/comparison. The inclusion criteria included English language literature with primary/secondary outcome objectives directly comparing ≥2 pain scales in acute pain (age: 13+). Study end points included interscale correlations, patient preferences, provider preferences, study author recommendations, and failure rates. RESULTS: Eight hundred seven studies were retrieved: A total of 42 studies were included. The visual analog scale (n = 42) was most studied, followed by NRS (n = 29), VRS (n = 27), and FPS (n = 11). 93.1% studies showed a high statistical correlation between VAS and NRS. Patients preferred NRS (n = 8/11), followed by FPS (n = 3/11), VRS (n = 2/11), and VAS (n = 1/11). Study authors recommended NRS/VAS (n = 8/19), VRS (n = 6/19), and FPS (n = 1/19). Providers preferred NRS (n = 2/3) and VRS (n = 1/3). The visual analog scale had the highest failure rate (n = 11/12). CONCLUSION: The numeric rating scale is most applicable for dermatologic surgery because of reported patient and provider preferences, lowest failure rates, and most frequent study author recommendations.


Subject(s)
Pain , Patient Satisfaction , Adolescent , Dermatologic Surgical Procedures/adverse effects , Humans , Pain/etiology , Pain Measurement/methods , Visual Analog Scale
2.
Telemed J E Health ; 27(7): 771-777, 2021 07.
Article in English | MEDLINE | ID: mdl-33074786

ABSTRACT

Background: Teledermatology offers an opportunity to continually deliver care during the coronavirus disease 2019 pandemic. Objective: To provide quantitative data about the use of teledermatology. Methods: Retrospective analysis of teledermatology consultations was performed from March 16 to May 1, 2020. The number/type of encounters, differences in diagnoses, and prescriptions between asynchronous and synchronous teledermatology visits were analyzed. Results: A total of 951 visits (36.2%) were asynchronous whereas 1,672 visits (63.8%) were synchronous. Only 131 (<5%) visits required an acute in-person follow-up. The diagnosis of acne was more frequent with asynchronous visits (p < 0.002, Bonferroni corrected). Antibiotics and nonretinoid acne medications were prescribed more with asynchronous visits, whereas immunomodulators and biologics were more commonly prescribed with synchronous visits (p < 0.02, Bonferroni corrected). Providers at our institution were split on preferred mode (54.2% synchronous, 45.8% asynchronous); however, synchronous visits were preferred for complex medical dermatology patients and return patients (p < 0.05). Limitations: This study is limited by being a single-center study. Conclusions: Asynchronous teledermatology was used more for acne management, whereas synchronous teledermatology was preferable to providers for complex medical dermatology. Postanalysis of the data collected led us to institute a hybridization of our asynchronous and synchronous teledermatology.


Subject(s)
COVID-19 , Dermatology , Skin Diseases , Telemedicine , Delivery of Health Care , Humans , Pandemics , Retrospective Studies , SARS-CoV-2
3.
Am J Dermatopathol ; 42(11): 854-857, 2020 Nov.
Article in English | MEDLINE | ID: mdl-32310862

ABSTRACT

Cutaneous melanomas may demonstrate a variety of histopathological features and genetic abnormalities. Melanomas that arise in the setting of blue nevi, also known as "malignant blue nevus" or melanoma ex blue nevus (MBN), share a similar histopathological and mutational profile with uveal melanoma. Most uveal melanomas show characteristic GNA11 or GNAQ mutations; additional BAP1 mutation or loss is associated with the highest risk of metastasis and worst prognosis. However, the significance of BAP1 loss in melanomas ex blue nevus remains unclear. We present a case of MBN arising from the scalp of a 21-year-old woman. The diagnosis was established on histopathological findings demonstrating a markedly atypical melanocytic proliferation with increased mitotic activity, necrosis, and a focus of angiolymphatic invasion. Immunohistochemical analysis demonstrated the absence of BAP1 nuclear expression within tumor cells. Next generation sequencing detected GNA11 Q209L mutation and BAP1 loss (chromosome 3p region loss), supporting the diagnosis. We reviewed another 21 MBN cases with reported BAP1 status from the literature. MBN with BAP1 loss presented at a younger average age (41 vs. 61 years), demonstrated larger average lesion thickness (9.0 vs. 7.3 mm), and had a higher rate of metastasis (50% vs. 33%) compared with BAP1-retained MBN. BAP1 expression studies may assist in the diagnosis and management of MBN, but further research is needed.


Subject(s)
GTP-Binding Protein alpha Subunits/genetics , Melanoma/genetics , Nevus, Blue/pathology , Skin Neoplasms/genetics , Tumor Suppressor Proteins/genetics , Ubiquitin Thiolesterase/genetics , Female , Humans , Melanoma/pathology , Nevus, Blue/genetics , Scalp/pathology , Skin Neoplasms/pathology , Young Adult
4.
J Cutan Pathol ; 47(7): 625-627, 2020 Jul.
Article in English | MEDLINE | ID: mdl-32022940

ABSTRACT

Sarcoidosis is a granulomatous condition with diverse clinical presentations, including neurological findings. It was previously hypothesized that perineural sarcoidal granulomas in the skin may be an explanation of small-fiber neuropathy. Herein, we present a case of a 55 year old female with anesthetic cutaneous lesions mimicking leprosy clinically and histopathologically and discuss the importance of this differential diagnosis.


Subject(s)
Peripheral Nerves/pathology , Sarcoidosis/diagnosis , Sarcoidosis/pathology , Skin Diseases/pathology , Diagnosis, Differential , Female , Granuloma/pathology , Humans , Leprosy/diagnosis , Middle Aged
5.
Dermatol Surg ; 46(10): 1286-1293, 2020 10.
Article in English | MEDLINE | ID: mdl-31895257

ABSTRACT

BACKGROUND: Inadequate pain reduction during anesthetic injection is a significant medical and surgical problem. Vibratory distraction reduces this pain; however, there are minimal data identifying those who respond best. OBJECTIVE: To quantify analgesia from vibration before anesthetic injection. MATERIALS AND METHODS: In this partially blinded, single-institution trial, adult participants were randomized to intervention (vibratory anesthetic device, VAD ON) or placebo (VAD OFF). Pain was assessed using the 11-point numeric rating scale (NRS). Relative reduction in NRS between VAD OFF and ON was used to identify minimum clinically important and substantially clinically important difference in pain. RESULTS: One hundred one tested sites from 87 subjects were assessed. Sixty-three percent were men with a median age of 66 years. From univariate analysis, males, subjects aged <60, and head and neck (HN) treated subjects had a significant reduction in NRS (p < .05). Multivariate analysis identified NRS reductions in females <60 (p = .012), males ≥70 (p = .002), females and males treated on HN (p = .048 and p = .035, respectively), and males ≥70 treated on HN (p = .012). Substantially clinically important difference (≥57% NRS reduction) included subjects <60, females <70, HN treatment aged 60 to 69, males ≥70, and females treated on HN. CONCLUSION: Vibratory anesthetic device reduces pain during anesthetic injection, primarily for HN treatments and older male subjects.


Subject(s)
Analgesia/methods , Anesthetics, Local/administration & dosage , Mohs Surgery/adverse effects , Pain, Procedural/prevention & control , Vibration/therapeutic use , Adult , Aged , Aged, 80 and over , Analgesia/instrumentation , Female , Humans , Injections, Subcutaneous/adverse effects , Male , Middle Aged , Pain Measurement , Pain, Procedural/diagnosis , Pain, Procedural/etiology , Treatment Outcome
6.
Cancer Immunol Immunother ; 69(2): 245-253, 2020 Feb.
Article in English | MEDLINE | ID: mdl-31676924

ABSTRACT

Schwann cells are the principal glial cells of the peripheral nervous system which maintain neuronal homeostasis. Schwann cells support peripheral nerve functions and play a critical role in many pathological processes including injury-induced nerve repair, neurodegenerative diseases, infections, neuropathic pain and cancer. Schwann cells are implicated in a wide range of diseases due, in part, to their ability to interact and modulate immune cells. We discuss the accumulating examples of how Schwann cell regulation of the immune system initiates and facilitates the progression of various diseases. Furthermore, we highlight how Schwann cells may orchestrate an immunosuppressive tumor microenvironment by polarizing and modulating the activity of the dendritic cells.


Subject(s)
Disease Susceptibility , Immunomodulation , Schwann Cells/immunology , Schwann Cells/metabolism , Animals , Biomarkers , Humans , Myelin Sheath/immunology , Myelin Sheath/metabolism , Signal Transduction
7.
JAMA Facial Plast Surg ; 21(6): 480-486, 2019 Dec 01.
Article in English | MEDLINE | ID: mdl-31513234

ABSTRACT

IMPORTANCE: Vibration has been shown to decrease injection site pain in patients; however, to date, this effect has not been assessed for patients who catastrophize pain (ie, patients who anticipate a higher pain level). The anticipation of a pain score greater than 4 on the 11-point Numeric Rating Scale (NRS) has been associated with an increase in a patient's perception of procedural pain. OBJECTIVE: To assess the efficacy of vibration during cutaneous anesthetic injection for dermatologic surgery for patients who catastrophize pain (NRS score >4) and patients who do not (NRS score ≤4). DESIGN, SETTING, AND PARTICIPANTS: Randomized, parallel-group clinical trial from June 19 to September 4, 2018, at a tertiary dermatologic surgery clinic among 87 adults undergoing cutaneous cancer removal surgery. Patients completed a preprocedural questionnaire detailing their baseline pain, anticipated pain, and drug use. Analysis was performed on an intent-to-treat basis. INTERVENTIONS: Use of a vibratory anesthetic device (VAD) on the treatment site prior to anesthetic injection in the on (VAD ON) or off (VAD OFF) mode. MAIN OUTCOMES AND MEASURES: Pain was reported using the 11-point NRS (where 0 indicates no pain and 11 indicates the worst pain imaginable). A minimum clinically important difference of 22% or more and a substantial clinically important difference of 57% or more were used to assess the efficacy of vibration in patient-reported NRS score during anesthetic injection (iNRS score). RESULTS: A total of 87 patients were included, with 101 unique events reported (among the unique events, 37 were reported in women and 64 were reported in men; mean [SD] age, 66.0 [11.3] years). The mean (confidence level [CL]) iNRS score for patients who catastrophized pain was 2.27 (0.66) compared with 1.44 (0.39) for patients who did not (P = .03). A 38.9% decrease in mean (CL) iNRS score was reported with VAD ON compared with VAD OFF in all participants (1.24 [0.38] vs 2.04 [0.54]). Patients who catastrophized pain reported a 25.5% decrease in mean (CL) iNRS score with VAD ON vs VAD OFF (1.91 [0.99] vs 2.57 [0.98]), and patients who did not reported a 79.4% decrease (1.02 [0.40] vs 1.84 [0.66]). VAD ON was the only statistically significant variable to affect iNRS score (F statistic, 2.741; P = .03). CONCLUSIONS AND RELEVANCE: This trial demonstrates that those who catastrophize pain prior to a procedure report a higher perceived level of pain. The application of vibration during local anesthetic injection resulted in a minimum clinically important difference in pain level for patients who catastrophize pain and a substantial clinically important difference in pain level for patients who do not. LEVEL OF EVIDENCE: 2. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03467685.


Subject(s)
Anesthetics, Local/administration & dosage , Injections/adverse effects , Pain Perception , Pain/etiology , Pain/prevention & control , Skin Neoplasms/surgery , Vibration , Adult , Aged , Aged, 80 and over , Catastrophization , Dermatologic Surgical Procedures , Humans , Middle Aged , Pain Measurement
8.
Anticancer Drugs ; 29(10): 929-934, 2018 11.
Article in English | MEDLINE | ID: mdl-30239424

ABSTRACT

During cancer progression, tumor cells interact with the neighboring environment, including neuronal tissue. The important influence of the nervous system on growth and metastasis of cancer is now widely accepted. As such, using medications that traditionally target the nervous system may be an avenue toward treating cancer. The focus of this review is to detail how several classes of medications, traditionally used to treat nervous system disorders, impact cancer. Specifically, we review the preclinical and clinical evidence that support the use of anti-ß-adrenergic, anticholinergic, antipsychotic, and antidepressant medications to treat some cancers. In addition, we discuss the use of ablative modalities, such as physical and chemical denervation, to treat cancer or protect against cancer development. Using the medications that target the nervous system to treat cancer is a promising addition to an existing therapy or an alternative treatment strategy. Furthermore, rapidly expanding basic science research in this area will likely yield novel cancer therapies that work by targeting the nervous system.


Subject(s)
Antineoplastic Agents/pharmacology , Neoplasms/drug therapy , Nervous System/drug effects , Animals , Disease Progression , Drug Design , Humans , Molecular Targeted Therapy , Neoplasms/pathology
9.
J Neurosci ; 36(9): 2617-22, 2016 Mar 02.
Article in English | MEDLINE | ID: mdl-26937003

ABSTRACT

AMPA and NMDA receptors are glutamate-gated ion channels that mediate fast excitatory synaptic transmission throughout the nervous system. In the continual presence of glutamate, AMPA and NMDA receptors containing the GluN2A or GluN2B subunit enter into a nonconducting, desensitized state that can impact synaptic responses and glutamate-mediated excitotoxicity. The process of desensitization is dramatically different between subtypes, but the basis for these differences is unknown. We generated an extensive sequence alignment of ionotropic glutamate receptors (iGluRs) from diverse animal phyla and identified a highly conserved motif, which we termed the "hydrophobic box," located at the extracellular interface of transmembrane helices. A single position in the hydrophobic box differed between mammalian AMPA and NMDA receptors. Surprisingly, we find that an NMDAR-to-AMPAR exchange mutation at this position in the rat GluN2A or GluN2B subunit had a dramatic and highly specific effect on NMDAR desensitization, making it AMPAR-like. In contrast, a reverse exchange mutation in AMPARs had minimal effects on desensitization. These experiments highlight differences in desensitization between iGluR subtypes and the highly specific contribution of the GluN2 subunit to this process. SIGNIFICANCE STATEMENT: Rapid communication between cells in the nervous system depends on ion channels that are directly activated by neurotransmitter molecules. Here, we studied ionotropic glutamate receptors (iGluRs), which are ion channels activated by the neurotransmitter glutamate. By comparing the sequences of a vast number of iGluR proteins from diverse animal species, assisted by available structural information, we identified a highly conserved motif. We showed that a single amino acid difference in this motif between mammalian iGluR subtypes has dramatic effects on receptor function. These results have implications in both the evolution of synaptic function, as well as the role of iGluRs in health and disease.


Subject(s)
Green Fluorescent Proteins/metabolism , Mutagenesis/genetics , Receptors, Ionotropic Glutamate/genetics , Animals , Biophysical Phenomena , Electric Stimulation , Glutamic Acid/pharmacology , Green Fluorescent Proteins/genetics , HEK293 Cells , Humans , Membrane Potentials/drug effects , Membrane Potentials/genetics , Mutation/genetics , Patch-Clamp Techniques , Protein Subunits/genetics , Protein Subunits/metabolism , Rats , Receptors, Ionotropic Glutamate/chemistry , Receptors, Ionotropic Glutamate/classification , Receptors, Ionotropic Glutamate/metabolism , Sequence Alignment , Transfection
11.
Nat Neurosci ; 17(7): 914-22, 2014 Jul.
Article in English | MEDLINE | ID: mdl-24859202

ABSTRACT

The fidelity of integration of pre- and postsynaptic activity by NMDA receptors (NMDARs) requires a match between agonist binding and ion channel opening. To address how agonist binding is transduced into pore opening in NMDARs, we manipulated the coupling between the ligand-binding domain (LBD) and the ion channel by inserting residues in a linker between them. We found that a single residue insertion markedly attenuated the ability of NMDARs to convert a glutamate transient into a functional response. This was largely a result of a decreased likelihood of the channel opening and remaining open. Computational and thermodynamic analyses suggest that insertions prevent the agonist-bound LBD from effectively pulling on pore lining elements, thereby destabilizing pore opening. Furthermore, this pulling energy was more prominent in the GluN2 subunit. We conclude that an efficient NMDAR-mediated synaptic response relies on a mechanical coupling between the LBD and the ion channel.


Subject(s)
Receptors, N-Methyl-D-Aspartate/physiology , Animals , Computer Simulation , Excitatory Amino Acid Agonists/metabolism , Glutamic Acid/metabolism , Ion Channel Gating/physiology , Kinetics , Ligands , Models, Molecular , Patch-Clamp Techniques , Rats , Receptors, N-Methyl-D-Aspartate/metabolism , Synapses/physiology , Thermodynamics
12.
J Neurosci ; 33(29): 12052-66, 2013 Jul 17.
Article in English | MEDLINE | ID: mdl-23864691

ABSTRACT

Glutamate-gated ion channels embedded within the neuronal membrane are the primary mediators of fast excitatory synaptic transmission in the CNS. The ion channel of these glutamate receptors contains a pore-lining transmembrane M3 helix surrounded by peripheral M1 and M4 helices. In the NMDA receptor subtype, opening of the ion channel pore, mediated by displacement of the M3 helices away from the central pore axis, occurs in a highly concerted fashion, but the associated temporal movements of the peripheral helices are unknown. To address the gating dynamics of the peripheral helices, we constrained the relative movements of the linkers that connect these helices to the ligand-binding domain using engineered cross-links, either within (intra-GluN1 or GluN2A) or between subunits. Constraining the peripheral linkers in any manner dramatically curtailed channel opening, highlighting the requirement for rearrangements of these peripheral structural elements for efficient gating to occur. However, the magnitude of this gating effect depended on the specific subunit being constrained, with the most dramatic effects occurring when the constraint was between subunits. Based on kinetic and thermodynamic analysis, our results suggest an asynchrony in the displacement of the peripheral linkers during the conformational and energetic changes leading to pore opening. Initially there are large-scale rearrangements occurring between the four subunits. Subsequently, rearrangements occur within individual subunits, mainly GluN2A, leading up to or in concert with pore opening. Thus, the conformational changes induced by agonist binding in NMDA receptors converge asynchronously to permit pore opening.


Subject(s)
Ion Channel Gating/physiology , Receptors, N-Methyl-D-Aspartate/metabolism , Animals , Binding Sites , HEK293 Cells , Humans , Models, Molecular , Protein Subunits/chemistry , Protein Subunits/metabolism , Rats , Receptors, N-Methyl-D-Aspartate/chemistry
13.
J Biol Chem ; 288(31): 22506-15, 2013 Aug 02.
Article in English | MEDLINE | ID: mdl-23782697

ABSTRACT

The NMDA-sensitive glutamate receptor is a ligand-gated ion channel that mediates excitatory synaptic transmission in the nervous system. Extracellular zinc allosterically regulates the NMDA receptor by binding to the extracellular N-terminal domain, which inhibits channel gating. Phosphorylation of the intrinsically disordered intracellular C-terminal domain alleviates inhibition by extracellular zinc. The mechanism for this functional effect is largely unknown. Proline is a hallmark of intrinsic disorder, so we used proline mutagenesis to modulate disorder in the cytoplasmic domain. Proline depletion selectively uncoupled zinc inhibition with little effect on receptor biogenesis, surface trafficking, or ligand-activated gating. Proline depletion also reduced the affinity for a PDZ domain involved in synaptic trafficking and affected small molecule binding. To understand the origin of these phenomena, we used single molecule fluorescence and ensemble biophysical methods to characterize the structural effects of proline mutagenesis. Proline depletion did not eliminate intrinsic disorder, but the underlying conformational dynamics were changed. Thus, we altered the form of intrinsic disorder, which appears sufficient to affect the biological activity. These findings suggest that conformational dynamics within the intrinsically disordered cytoplasmic domain are important for the allosteric regulation of NMDA receptor gating.


Subject(s)
Cytoplasm/metabolism , Receptors, N-Methyl-D-Aspartate/physiology , Allosteric Regulation , Electrophoresis, Polyacrylamide Gel , Fluorescence Resonance Energy Transfer , HEK293 Cells , Humans , Protein Binding , Receptors, N-Methyl-D-Aspartate/metabolism , Solubility
14.
J Neurosci ; 33(23): 9840-5, 2013 Jun 05.
Article in English | MEDLINE | ID: mdl-23739980

ABSTRACT

Most fast excitatory synaptic transmission in the nervous system is mediated by glutamate acting through ionotropic glutamate receptors (iGluRs). iGluRs (AMPA, kainate, and NMDA receptor subtypes) are tetrameric assemblies, formed as a dimer of dimers. Still, the mechanism underlying tetramerization--the necessary step for the formation of functional receptors that can be inserted into the plasma membrane--is unknown. All eukaryotic compared to prokaryotic iGluR subunits have an additional transmembrane segment, the M4 segment, which positions the physiologically critical C-terminal domain on the cytoplasmic side of the membrane. AMPA receptor (AMPAR) subunits lacking M4 do not express on the plasma membrane. Here, we show that these constructs are retained in the endoplasmic reticulum, the major cellular compartment mediating protein oligomerization. Using approaches to assay the native oligomeric state of AMPAR subunits, we find that subunits lacking M4 or containing single amino acid substitutions along an "interacting" face of the M4 helix that block surface expression no longer tetramerize in either homomeric or heteromeric assemblies. In contrast, subunit dimerization appears to be largely intact. These experiments define the M4 segment as a unique functional unit in AMPARs that is required for the critical dimer-to-tetramer transition.


Subject(s)
Eukaryotic Cells/chemistry , Protein Multimerization/physiology , Receptors, AMPA/chemistry , Animals , Cell Membrane/chemistry , Cell Membrane/physiology , Eukaryotic Cells/physiology , HEK293 Cells , Humans , Protein Structure, Secondary , Protein Subunits/chemistry , Protein Subunits/physiology , Rats , Receptors, AMPA/physiology
15.
Biophys J ; 101(10): 2389-98, 2011 Nov 16.
Article in English | MEDLINE | ID: mdl-22098737

ABSTRACT

NMDA receptors are glutamate-activated ion channel complexes central to the functioning of the mammalian nervous system. Opening of the NMDA receptor ion channel pore is initiated by agonist-induced conformational changes in the extracellular ligand-binding domain (LBD) but the dynamic mechanism of this process remains unresolved. We studied how a disulfide bond in the obligatory GluN1 subunit-the sole site of redox modulation in NMDA receptors-controls this activation gating mechanism. This disulfide bond is located in the hinge region of the LBD, and presumably constrains agonist-induced cleft closure of the clamshell-like LBD. Elimination of this bond, by either DTT-mediated reduction or mutagenesis, enhances gating efficiency such that pore opening now occurs with higher frequency and longer duration. The most prominent effect was to shift opening modes to long duration openings reminiscent of a high P(o) gating mode that the NMDA receptor exhibits under ambient oxidizing conditions. In terms of preopen gating steps, elimination of this bond has effects only on the fast gating step consistent with this step being GluN1-specific and reflecting GluN1 gating movements immediately before channel opening. Overall, our results suggest that the dynamics of the GluN1 LBD have strong effects on late pore opening steps including regulating the duration of pore opening. This redox-mediated gating modulation could be an underlying mechanism of NMDA receptor malfunction in redox-dependent disease states and presents a potential target of pharmacologic action.


Subject(s)
Ion Channel Gating , Protein Subunits/metabolism , Receptors, N-Methyl-D-Aspartate/metabolism , Animals , Cysteine/metabolism , Disulfides/metabolism , Dithiothreitol/pharmacology , Ion Channel Gating/drug effects , Kinetics , Ligands , Oxidation-Reduction/drug effects , Protein Structure, Tertiary , Rats , Time Factors , Xenopus
16.
J Biol Chem ; 286(46): 40205-18, 2011 Nov 18.
Article in English | MEDLINE | ID: mdl-21930708

ABSTRACT

Ionotropic glutamate receptors (GluRs) are ligand-gated ion channels with a modular structure. The ion channel itself shares structural similarity, albeit an inverted membrane topology, with P-loop channels. Like P-loop channels, prokaryotic GluR subunits (e.g. GluR0) have two transmembrane segments. In contrast, eukaryotic GluRs have an additional transmembrane segment (M4), located C-terminal to the ion channel core. However, the structural/functional significance of this additional transmembrane segment is poorly defined. Although topologically similar to GluR0, mammalian AMPA receptor (GluA1) subunits lacking the M4 segment do not display surface expression. This lack of expression is not due to the M4 segment serving as an anchor to the ligand-binding domain because insertion of an artificial polyleucine transmembrane segment does not rescue surface expression. Specific interactions between M4 and the ligand-binding domain are also unlikely because insertion of polyglycines into the linker connecting them has no deleterious effects on function or surface expression. However, tryptophan and cysteine scanning mutagenesis of the M4 segment, as well as recovery of function in the polyleucine background, defined a unique face of the M4 helix that is required for GluR surface expression. In the AMPA receptor structure, this face forms intersubunit contacts with the transmembrane helices of the ion channel core (M1 and M3) from another subunit within the homotetramer. Thus, our experiments show that a highly specific interaction of the M4 segment with an adjacent subunit is required for surface expression of AMPA receptors. This interaction may represent a mechanism for regulating AMPA receptor biogenesis.


Subject(s)
Gene Expression Regulation/physiology , Receptors, AMPA/biosynthesis , alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid , Animals , HEK293 Cells , Humans , Mutagenesis , Protein Structure, Secondary , Protein Structure, Tertiary , Receptors, AMPA/agonists , Receptors, AMPA/genetics , Xenopus laevis
SELECTION OF CITATIONS
SEARCH DETAIL
...