EADV Task Force Pruritus White Paper on chronic pruritus and chronic prurigo: Current challenges and future solutions

Chronic pruritus (CP) is frequent in general medicine and the most common complaint in general dermatology. The prevalence of CP is expected to rise in the future due to the ageing population. The clinical presentation, underlying aetiology and treatment strategy of CP are heterogeneous. Also, individual treatment aims and physical, psychic and economic burdens of patients might vary. Chronic prurigo (CPG) is the most severe disease in the chronic pruritus spectrum, being associated with long-standing scratch-induced skin lesions and a therapy refractory itch-scratch-cycle. It is thus important to raise disease awareness for CP and CPG in the general public and among decision-makers in the health system. Further, there is a need to support a rational clinical framework to optimize both diagnostics and therapeutics. Currently, there is still a shortcoming regarding approved therapies and understanding CP/CPG as severe medical conditions. Therefore, the EADV Task Force Pruritus decided to publish this white paper based on several consensus meetings. The group consented on the following goals: (a) ensure that CP is recognized as a serious condition, (b) increase public awareness and understanding of CP and CPG as chronic and burdensome diseases that can greatly affect a person's quality of life, (c) clarify that in most cases CP and CPG are non-communicable and not caused by a psychiatric disease, (d) improve the support and treatment given to patients with CP to help them manage their disease and (e) publicize existing therapies including current guidelines. We aim to point to necessary improvements in access and quality of care directed to decision-makers in health policy, among payers and administrations as well as in practical care.

Dermatological patients with itch report more stress, stigmatization experience, anxiety and depression compared to patients without itch: Results from a European multi-centre study

BACKGROUND

Itch as the most common symptom in dermatology has been shown to be related to psychological factors such as stress, anxiety and depression. Moreover, associations were found between perceived stigmatization and itch. However, studies investigating the differences between patients with dermatoses with and without itch regarding perceived stress, stigmatization, anxiety and depression are missing. Therefore, one of the aims of the second study of the European Society for Dermatology and Psychiatry (ESDaP study II) was to investigate these relationships in a large cohort of patients with different itchy dermatoses.

RESULTS

3399 patients with 14 different itchy dermatoses were recruited at 22 centres in 17 European countries. They filled in questionnaires to assess perceived stigmatization, stress, signs of clinically relevant anxiety or depression, itch-related quality of life, the overall health status, itch duration, frequency and intensity. The most significant association between the severity of itching and the perception of stress was observed among individuals with rosacea (correlation coefficient r = 0.314). Similarly, the strongest links between itch intensity and experiences of stigmatization, anxiety, and depression were found in patients with seborrheic dermatitis (correlation coefficients r = 0.317, r = 0.356, and r = 0.400, respectively). Utilizing a stepwise linear regression analysis, it was determined that within the entire patient cohort, 9.3% of the variation in itch intensity could be accounted for by factors including gender, levels of anxiety, depression, and perceived stigmatization. Females and individuals with elevated anxiety, depression, and perceived stigmatization scores reported more pronounced itch intensities compared to those with contrary attributes.

CONCLUSION

This study underscores the connection between experiencing itch and its intensity and the psychological strain it places on individuals. Consequently, psychological interventions should encompass both addressing the itch itself and the interconnected psychological factors. In specific cases, it becomes imperative for dermatologists to direct individuals towards suitable healthcare resources to undergo further psychological assessment.

Discovery and Optimization of DNA Gyrase and Topoisomerase IV Inhibitors with Potent Activity against Fluoroquinolone-Resistant Gram-Positive Bacteria

Herein, we describe the discovery and optimization of a novel series that inhibits bacterial DNA gyrase and topoisomerase IV via binding to, and stabilization of, DNA cleavage complexes. Optimization of this series led to the identification of compound 25, which has potent activity against Gram-positive bacteria, a favorable in vitro safety profile, and excellent in vivo pharmacokinetic properties. Compound 25 was found to be efficacious against fluoroquinolone-sensitive Staphylococcus aureus infection in a mouse thigh model at lower doses than moxifloxacin. An X-ray crystal structure of the ternary complex formed by topoisomerase IV from Klebsiella pneumoniae, compound 25, and cleaved DNA indicates that this compound does not engage in a water-metal ion bridge interaction and forms no direct contacts with residues in the quinolone resistance determining region (QRDR). This suggests a structural basis for the reduced impact of QRDR mutations on antibacterial activity of 25 compared to fluoroquinolones.

Pruritus Intensity Scales across Europe: a prospective validation study

BACKGROUND

Chronic pruritus (CP) is a subjective symptom, and it is necessary to assess its intensity with validated patient-reported outcome tools in order to allow determination of the treatment course.

OBJECTIVES

So far, the itch intensity scales were validated in small cohorts and in single languages. Here, we report the validation of the numerical rating scale, the verbal rating scale and the visual analogue scale for the worst and average pruritus intensity in the last 24h in several languages across Europe and across different pruritic dermatoses.

METHODS

After professional translation, the intensity scales were digitized for use as a tablet computer application. Validation was performed in clinics for Dermatology in Austria, France, Germany, Italy, Poland, Russia, Spain, Switzerland and Turkey.

RESULTS

A total of 547 patients with contact dermatitis, chronic nodular prurigo, psoriasis vulgaris, lichen planus or cutaneous T-cell lymphoma were included. The intensity scales showed a high level of reproducibility and inter-correlations with each other. The correlation with the Dermatology Life Quality Index was weak to strong in nearly all countries and dermatoses with the exception of France and patients with chronic nodular prurigo, for which no statistically significant correlations were found.

CONCLUSIONS

The numerical rating scale, the verbal rating scale und the visual analogue scales are valid instruments with good reproducibility and internal consistency in German (Germany, Austria, Switzerland), French, Italian, Polish, Russian, Spanish and Turkish for different pruritic dermatoses. VAS worst was the best reproducible and consistent measuring instrument in all countries.

Google search trends for itch in Europe: a retrospective longitudinal study

BACKGROUND

Itch is a common symptom in the general population. Affected individuals often do not seek medical consultation and rely on Internet searches to obtain information regarding their itch.

OBJECTIVES

The aim of this study was to attain insights into common concerns of the general population regarding itch can by analysing itch-related Internet search behaviour.

METHODS

Google AdWords Keyword Planner was used to assess search volumes for itch-related terms in 15 European countries between September 2014 and August 2018. All identified keywords were qualitatively categorized. Itch-related terms were descriptively analysed and are shown as number of searches/100 000 inhabitants.

RESULTS

The search volume for the keyword 'itch' per 100 000 inhabitants was highest in Northern Europe, followed by Eastern, Central and Southern Europe. In 4/15 countries, itch was searched for more often in the autumn/winter months compared to in the spring/summer months. Most itch-related terms were related to dermatological conditions such as inflammatory skin diseases (e.g. psoriasis, atopic dermatitis), allergic or immunologic conditions (e.g. urticaria), and infectious diseases or infestations (e.g. scabies). In terms of body location, genitoanal itch dominated the searches. Symptoms and signs related to itch, possible non-dermatological aetiologies, and treatment options were also among the most searched terms.

CONCLUSIONS

These analyses provided for the first time insights into the search behaviour patterns related to itch across Europe. People from Northern and Eastern Europe are more likely to seek online information regarding itch. Causes for the itch, especially dermatological conditions, and genitoanal itch are the most important concerns for Internet users. This unconventional and inexpensive method identifies medical needs of people beyond the medical setting, including people who do not seek medical consultation. Accordingly, the data could be used to guide public health interventions and manage respective inhabitants' medical needs.

Topoisomerase Inhibitors Addressing Fluoroquinolone Resistance in Gram-Negative Bacteria

Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region.

Chronic nodular prurigo: clinical profile and burden. A European cross-sectional study

BACKGROUND

Chronic nodular prurigo (CNPG) is a condition characterized by chronic itch, a prolonged scratching behaviour and the presence of pruriginous nodules. A comprehensive understanding of this condition, especially regarding its clinical characteristics and impact on quality of life is still lacking.

OBJECTIVES

Aim of this pan-European multicentre cross-sectional study was to establish the clinical profile of CNPG, including its associated burden.

METHODS

Fifteen centres from 12 European countries recruited CNPG patients presenting at the centre or using the centres' own databases. Patients were asked to complete a questionnaire in paper or electronic format. Demography, current co-morbidities, underlying disease, itch intensity, additional sensory symptoms, quality of life, highest burden and emotional experience of itch were assessed.

RESULTS

A total of 509 patients (210 male, median age: 64 years [52; 72]) were enrolled. Of these, 406 reported itch and CNPG lesions in the previous 7 days and qualified to complete the whole questionnaire. We recorded moderate to severe worst itch intensity scores in the previous 24 h. Scores were higher in patients with lower educational levels and those coming from Eastern or Southern Europe. Most patients experience itch often or always (71%) and report that their everyday life is negatively affected (53%). Itch intensity was considered to be the most burdensome aspect of the disease by 49% of the patients, followed by the visibility of skin lesions (21%) and bleeding of lesions (21%). The majority of patients was unaware of an underlying condition contributing to CNPG (64%), while psychiatric diseases were the conditions most often mentioned in association with CNPG (19%).

CONCLUSIONS

This multicentre cross-sectional study shows that itch is the dominant symptom in CNPG and reveals that the profile of the disease is similar throughout Europe.

Cross-European validation of the ItchyQoL in pruritic dermatoses

BACKGROUND

Chronic pruritus (CP) is a frequently occurring symptom in inflammatory dermatoses, causing a high burden and limitations to health-related quality of life (HRQoL).

OBJECTIVE

The ItchyQoL was developed to assess the impairment to HRQoL in patients with CP. However, it has only been validated in English and German. Here, we report the validation in several languages across Europe.

METHODS

After professional translation, the versions of ItchyQoL were digitized for use as a tablet application. Validation was performed in clinics for dermatology in Austria, France, Germany, Italy, Poland, Russia, Spain, Switzerland and Turkey.

RESULTS

Five hundred and thirty-five patients with either contact dermatitis, chronic prurigo - nodular type, psoriasis vulgaris, lichen planus or mycosis fungoides/Sézary syndrome and with CP ≥ 3 on the numerical rating scale were included. ItchyQoL showed a high level of consistency (Cronbach's-α, all: 0.95) and test-retest reliability (intraclass correlation: 0.91). It strongly correlated with the Dermatology Life Quality Index (r = 0.72, P < 0.001) and moderately correlated with itch intensity scales in the study population (visual analogue scale r = 0.46; numerical rating scale r = 0.51; verbal rating scale r = 0.51, for all: P < 0.001).

CONCLUSION

ItchyQoL is now also validated in French, Italian, Polish, Russian, Spanish and Turkish and can be used in clinical trials in countries speaking these languages.

The self-assessed psychological comorbidities of prurigo in European patients: a multicentre study in 13 countries

BACKGROUND

Prurigo is defined by the presence of chronic pruritus and multiple localized or generalized pruriginous lesions.

OBJECTIVE

The aim of this study was to assess the psychological burden of prurigo in patients of European countries.

METHODS

In this multicentre European study, 3635 general dermatology outpatients and 1359 controls were included. Socio-demographic data and answers to questionnaires (regarding quality of life, general health, anxiety and depression and suicidal ideation) were collected.

RESULTS

There were 27 patients with prurigo; of these, 63% were men, and the mean age was 58.6 years. Among patients with prurigo, 10 of 27 (37%) suffered from anxiety and 8 of 27 (29%) from depression. Suicidal ideation was reported in 5 of 27 (19%) patients, and for four of these five patients, suicidal ideation was related to their skin disease. These frequencies were higher in the 10 commonest dermatological diseases (including psoriasis, atopic dermatitis and leg ulcers). The impact on quality of life was severe, with a mean Dermatologic Life Quality Index (DLQI) of 12.4, with an extreme impact on quality of life for 23% of patients and a very large impact for 27% of patients.

CONCLUSION

The psychological comorbidities of prurigo are common, greater than those of other skin diseases, and their impact on quality of life is significant. Thus, it is important to study this condition and to find new treatments.

Dermatologists across Europe underestimate depression and anxiety: results from 3635 dermatological consultations

BACKGROUND

It was recently demonstrated that a significant number of patients with common skin diseases across Europe are clinically depressed and anxious. Studies have shown that physicians not trained as psychiatrists underdiagnose depression. This has not been explored among dermatologists.

OBJECTIVES

To estimate the concordance between clinical assessment of depression and anxiety by a dermatologist and assessment with the Hospital Anxiety and Depression Scale (HADS).

METHODS

The study was an observational cross-sectional multicentre study of prevalent cases of skin diseases in 13 countries in Europe. Consecutive patients were recruited in outpatient clinics and filled in questionnaires prior to clinical examination by a dermatologist who reported any diagnosis of skin disease and signs of mood disorders.

RESULTS

Analysis of the 3635 consultations showed that the agreement between dermatologist and HADS was poor to fair (lower than 0·4) for all diagnosis categories. The true-positive rate (represented by the percentage of dermatologists recognizing signs of depression or anxiety in patients with depression or anxiety as defined by a HADS value ≥ 11) was 44·0% for depression and 35·6% for anxiety. The true negative rate (represented by the percentage of dermatologists not detecting signs of depression or anxiety in non-depressed or non-anxious patients defined by HADS-value < 11) was 88.8% for depression and 85.7% for anxiety.

CONCLUSIONS

Dermatologists in Europe tend to underestimate mood disorders. The results suggest that further training for dermatologists to improve their skills in diagnosing depression and anxiety might be appropriate. When present, the psychological suffering of patients with dermatological conditions needs to be addressed.

The burden of common skin diseases assessed with the EQ5D™: a European multicentre study in 13 countries

BACKGROUND

Generic instruments measuring health-related quality of life (HRQoL), like EQ5D™, enable comparison of skin diseases with healthy populations and nondermatological medical conditions, as well as calculation of utility data.

OBJECTIVES

To measure HRQoL in patients with common skin diseases and healthy controls across Europe using the EQ5D.

METHODS

This multicentre observational cross-sectional study was conducted in 13 European countries. Each dermatology clinic recruited at least 250 consecutive adult outpatients to complete questionnaires, including the EQ5D.

RESULTS

There were 5369 participants (4010 patients and 1359 controls). Mean ± SD self-rated health state reported by patients was 69·9 ± 19·7; for controls it was 82·2 ± 15·5. When adjusted for confounding factors, including comorbidity, mean patient EQ visual analogue scores were 10·5 points lower than for controls (standardized β = -0·23). Odds ratio with 95% confidence interval for impairment in all five dimensions of EQ5D adjusted for confounders was doubled for patients compared with controls. Patients with hidradenitis suppurativa (HS), blistering conditions, leg ulcers, psoriasis and eczemas had the highest risk for reduction in HRQoL in most dimensions (2-10-fold). Data on differences of impairment by dimensions offer new insights.

CONCLUSIONS

This study confirms the large impact skin conditions have on patients' well-being, differentiating between aspects of HRQoL. Patients with HS, blistering diseases, leg ulcers, infections and most chronic skin diseases reported reduced HRQoL compared with patients with chronic obstructive lung disease, diabetes mellitus, cardiovascular disease and cancers. These findings are important in the prioritization of resource allocation between medical fields and within dermatological subspecialities.

The acid-sensitive, anesthetic-activated potassium leak channel, KCNK3, is regulated by 14-3-3β-dependent, protein kinase C (PKC)-mediated endocytic trafficking

The acid-sensitive neuronal potassium leak channel, KCNK3, is vital for setting the resting membrane potential and is the primary target for volatile anesthetics. Recent reports demonstrate that KCNK3 activity is down-regulated by PKC; however, the mechanisms responsible for PKC-induced KCNK3 down-regulation are undefined. Here, we report that endocytic trafficking dynamically regulates KCNK3 activity. Phorbol esters and Group I metabotropic glutamate receptor (mGluR) activation acutely decreased both native and recombinant KCNK3 currents with concomitant KCNK3 surface losses in cerebellar granule neurons and cell lines. PKC-mediated KCNK3 internalization required the presence of both 14-3-3β and a novel potassium channel endocytic motif, because depleting either 14-3-3β protein levels or ablating the endocytic motif completely abrogated PKC-regulated KCNK3 trafficking. These results demonstrate that neuronal potassium leak channels are not static membrane residents but are subject to 14-3-3β-dependent regulated trafficking, providing a straightforward mechanism to modulate neuronal excitability and synaptic plasticity by Group I mGluRs.

Post-translational N-glycosylation of type I transmembrane KCNE1 peptides: implications for membrane protein biogenesis and disease

N-Glycosylation of membrane proteins is critical for their proper folding, co-assembly and subsequent matriculation through the secretory pathway. Here, we examine the kinetics of N-glycan addition to type I transmembrane KCNE1 K(+) channel β-subunits, where point mutations that prevent N-glycosylation at one consensus site give rise to disorders of the cardiac rhythm and congenital deafness. We show that KCNE1 has two distinct N-glycosylation sites: a typical co-translational site and a consensus site ∼20 residues away that unexpectedly acquires N-glycans after protein synthesis (post-translational). Mutations that ablate the co-translational site concomitantly reduce glycosylation at the post-translational site, resulting in unglycosylated KCNE1 subunits that cannot reach the cell surface with their cognate K(+) channel. This long range inhibition is highly specific for post-translational N-glycosylation because mutagenic conversion of the KCNE1 post-translational site into a co-translational site restored both monoglycosylation and anterograde trafficking. These results directly explain how a single point mutation can prevent N-glycan attachment at multiple sites, providing a new biogenic mechanism for human disease.

O-glycosylation of the cardiac I(Ks) complex

Post-translational modifications of the KCNQ1–KCNE1 (Kv7) K+ channel complex are vital for regulation of the cardiac IKs current and action potential duration. Here, we show the KCNE1 regulatory subunit is O-glycosylated with mucin-type glycans in vivo. As O-linked glycosylation sites are not recognizable by sequence gazing, we designed a novel set of glycosylation mutants and KCNE chimeras and analysed their glycan content using deglycosylation enzymes. Our results show that KCNE1 is exclusively O-glycosylated at Thr-7, which is also required for N-glycosylation at Asn-5. For wild type KCNE1, the overlapping N- and O-glycosylation sites are innocuous for subunit biogenesis; however, mutation of Thr-7 to a non-hydroxylated residue yielded mostly unglycosylated protein and a small fraction of mono-N-glycosylated protein. The compounded hypoglycosylation was equally deleterious for KCNQ1–KCNE1 cell surface expression, demonstrating that KCNE1 O-glycosylation is a post-translational modification that is integral for the proper biogenesis and anterograde trafficking of the cardiac IKs complex. The enzymatic assays and panel of glycosylation mutants used here will be valuable for identifying the different KCNE1 glycoforms in native cells and determining the roles N- and O-glycosylation play in KCNQ1–KCNE1 function and localization in cardiomyocytes,

Chemical control of metabolically-engineered voltage-gated K+ channels

Metabolic oligosaccharide engineering is a powerful approach for installing unnatural glycans with unique functional groups into the glycocalyx of living cells and animals. Using this approach, we showed that K(+) channel complexes decorated with thiol-containing sialic acids were irreversibly inhibited with scorpion toxins bearing a pendant maleimide group. Irreversible inhibition required a glycosylated K(+) channel subunit and was completely reversible with mild reductant when the tether connecting the toxin to the maleimide contained a disulfide bond. Cleavage of the disulfide bond not only restored function, but delivered a biotin moiety to the modified K(+) channel subunit, providing a novel approach for preferentially labeling wild type K(+) channel complexes functioning in cells.

Identification of a protein-protein interaction between KCNE1 and the activation gate machinery of KCNQ1

KCNQ1 channels assemble with KCNE1 transmembrane (TM) peptides to form voltage-gated K⁺ channel complexes with slow activation gate opening. The cytoplasmic C-terminal domain that abuts the KCNE1 TM segment has been implicated in regulating KCNQ1 gating, yet its interaction with KCNQ1 has not been described. Here, we identified a protein–protein interaction between the KCNE1 C-terminal domain and the KCNQ1 S6 activation gate and S4–S5 linker. Using cysteine cross-linking, we biochemically screened over 300 cysteine pairs in the KCNQ1–KCNE1 complex and identified three residues in KCNQ1 (H363C, P369C, and I257C) that formed disulfide bonds with cysteine residues in the KCNE1 C-terminal domain. Statistical analysis of cross-link efficiency showed that H363C preferentially reacted with KCNE1 residues H73C, S74C, and D76C, whereas P369C showed preference for only D76C. Electrophysiological investigation of the mutant K⁺ channel complexes revealed that the KCNQ1 residue, H363C, formed cross-links not only with KCNE1 subunits, but also with neighboring KCNQ1 subunits in the complex. Cross-link formation involving the H363C residue was state dependent, primarily occurring when the KCNQ1–KCNE1 complex was closed. Based on these biochemical and electrophysiological data, we generated a closed-state model of the KCNQ1–KCNE1 cytoplasmic region where these protein–protein interactions are poised to slow activation gate opening.

Rearrangements in the relative orientation of cytoplasmic domains induced by a membrane-anchored protein mediate modulations in Kv channel gating

Interdomain interactions between intracellular N and C termini have been described for various K(+) channels, including the voltage-gated Kv2.1, and suggested to affect channel gating. However, no channel regulatory protein directly affecting N/C interactions has been demonstrated. Most Kv2.1 channel interactions with regulatory factors occur at its C terminus. The vesicular SNARE that is also present at a high concentration in the neuronal plasma membrane, VAMP2, is the only protein documented to affect Kv2.1 gating by binding to its N terminus. As its binding target has been mapped near a site implicated in Kv2.1 N/C interactions, we hypothesized that VAMP2 binding to the N terminus requires concomitant conformational changes in the C terminus, which wraps around the N terminus from the outside, to give VAMP2 access. Here, we first determined that the Kv2.1 N terminus, although crucial, is not sufficient to convey functional interaction with VAMP2, and that, concomitant to its binding to the "docking loop" at the Kv2.1 N terminus, VAMP2 binds to the proximal part of the Kv2.1 C terminus, C1a. Next, using computational biology approaches (ab initio modeling, docking, and molecular dynamics simulations) supported by molecular biology, biochemical, electrophysiological, and fluorescence resonance energy transfer analyses, we mapped the interaction sites on both VAMP2 and Kv2.1 and found that this interaction is accompanied by rearrangements in the relative orientation of Kv2.1 cytoplasmic domains. We propose that VAMP2 modulates Kv2.1 inactivation by interfering with the interaction between the docking loop and C1a, a mechanism for gating regulation that may pertain also to other Kv channels.

Formation of the full SNARE complex eliminates interactions of its individual protein components with the Kv2.1 channel

Previously, we have demonstrated physical and functional interactions of the voltage-gated potassium channel Kv2.1 with the plasma membrane protein components of the exocytotic SNARE complex, syntaxin 1A, and the t-SNARE, syntaxin 1A/SNAP-25, complex. Importantly, the physical interaction of Kv2.1 with syntaxin was shown to be involved in the facilitation of secretion from PC12 cells, which was independent of potassium currents. Recently, we showed that also VAMP2, the vesicular SNARE, interacts physically and functionally with Kv2.1. Here, we first set out to test the interaction of the full SNARE, syntaxin/SNAP-25/VAMP2, complex with the channel. Using the interaction of VAMP2 with Kv2.1 in Xenopus oocytes as a probe, we showed that coexpression of the t-SNARE complex with VAMP2 abolished the VAMP2 effect on channel inactivation and reduced the amount of VAMP2 that coprecipitated with Kv2.1. Further, in vitro pull down assays showed that the full SNARE complex failed to interact with Kv2.1 N- and C-termini in tandem, in contrast to the individual SNARE components. This suggests that the interactions of the SNARE components with Kv2.1 are abolished upon their recruitment into a full SNARE complex, which does not interact with the channel. Other important findings arising from the in vitro study are that the t-SNARE complex, in addition to syntaxin, interacts with a specific C-terminal channel domain, C1a, shown to mediate the facilitation of release by Kv2.1 and that the presence of Kv2.1 N-terminus has crucial contribution to these interactions. These findings provide important insights into the understanding of the complex molecular events involved in the novel phenomenon of secretion facilitation in neuroendocrine cells by Kv2.1.

VAMP2 interacts directly with the N terminus of Kv2.1 to enhance channel inactivation

Recently, we demonstrated that the Kv2.1 channel plays a role in regulated exocytosis of dense-core vesicles (DCVs) through direct interaction of its C terminus with syntaxin 1A, a plasma membrane soluble NSF attachment receptor (SNARE) component. We report here that Kv2.1 interacts with VAMP2, the vesicular SNARE partner that is also present at high concentration in neuronal plasma membrane. This is the first report of VAMP2 interaction with an ion channel. The interaction was demonstrated in brain membranes and characterized using electrophysiological and biochemical analyses in Xenopus oocytes combined with an in vitro binding analysis and protein modeling. Comparative study performed with wild-type and mutant Kv2.1, wild-type Kv1.5, and chimeric Kv1.5N/Kv2.1 channels revealed that VAMP2 enhanced the inactivation of Kv2.1, but not of Kv1.5, via direct interaction with the T1 domain of the N terminus of Kv2.1. Given the proposed role for surface VAMP2 in the regulation of the vesicle cycle and the important role for the sustained Kv2.1 current in the regulation of dendritic calcium entry during high-frequency stimulation, the interaction of VAMP2 with Kv2.1 N terminus may contribute, alongside with the interaction of syntaxin with Kv2.1 C terminus, to the activity dependence of DCV release.