The generation of pacemaker activity in heart and brain is mediated by hyperpolarization-activated cation channels that are directly regulated by cyclic nucleotides. We previously cloned a novel member of the voltage-gated K channel family from mouse brain (mBCNG-1) that contained a carboxy-terminal cyclic nucleotide-binding domain (Santoro et al., 1997) and hence proposed it to be a candidate gene for pacemaker channels. Heterologous expression of mBCNG-1 demonstrates that it does indeed code for a channel with properties indistinguishable from pacemaker channels in brain and similar to those in heart. Three additional mouse genes and two human genes closely related to mBCNG-1 display unique patterns of mRNA expression in different tissues, including brain and heart, demonstrating that these channels constitute a widely expressed gene family.

Scientific instruments and computer simulations are creating vast data stores that require new scientific methods to analyze and organize the data. Data volumes are approximately doubling each year. Since these new instruments have extraordinary precision, the data quality is also rapidly improving. Analyzing this data to find the subtle effects missed by previous studies requires algorithms that can simultaneously deal with huge datasets and that can find very subtle effects --- finding both needles in the haystack and finding very small haystacks that were undetected in previous measurements.

Cyclic nucleotide-gated ion channels are composed of four pore-forming subunits. Binding of cyclic nucleotide to a site in the intracellular carboxyl terminus of each subunit leads to channel activation. Since there are four subunits, four binding events are possible. In this study, we investigate the effects of individual binding events on activation by studying channels containing one, two, three, or four functional binding sites. The binding of a single ligand significantly increases opening, although four ligands are required for full activation. The data are inconsistent with models in which the four subunits activate in a single concerted step (Monod-Wyman-Changeux model) or in four independent steps (Hodgkin-Huxley model). Instead, the four subunits may associate and activate as two independent dimers.

Cyclic nucleotide-gated (CNG) ion channels are multimeric structures containing at least two subunits. However, the total number of subunits per functional channel is unknown. To determine the subunit stoichiometry of CNG ion channels, we have coexpressed the 30 pS conductance bovine retinal channel (RET) with an 85 pS conductance chimeric retinal channel containing the catfish olfactory channel P region (RO133). When RO133 and RET monomers are coexpressed, channels with four distinct intermediate conductances are observed. Dimer constructs reveal that two of these conductance levels arise from channels with the same subunit composition (2 RO133:2 RET) but distinct subunit order (like subunits adjacent to each other versus like subunits across from each other). Thus, the data demonstrate that cyclic nucleotide-gated ion channels are tetrameric like the related voltage-gated potassium ion channels; the order of subunits affects the conductance of the channel; and the channel has 4-fold symmetry in which four asymmetric subunits assemble head to tail around a central axis.

Background The aim of the study is to analyze potential prognostic factors and to evaluate therapy strategies regarding clinical outcome in patients with eccrine porocarcinoma (EPC) of the head and neck. Methods One hundred and sixteen EPC cases from ninety studies and four authors' EPC cases were included in the meta‐analysis. Results At an average follow up of 20.48 months, the 3‐year overall survival and regional recurrence rate were 70.3% and 19.0%, respectively. Patients without surgical treatment had a significantly worse 3‐year overall survival. Mohs microscopic surgery led to significantly less occurrence of regional recurrences compared to wide excision. An ulcerating lesion, high mitotic activity, and lymphovascular invasion were significant prognostic factors. Conclusion Surgical resection is the cornerstone in the therapy of EPC and represents the therapeutic modality that offers the best chance of disease‐free survival. Due to the high probability of recurrence, close follow‐ups are strongly recommended.

Objective/Hypothesis This study aims to determine the association between parosmia and clinically relevant recovery of olfactory function in patients with post‐infectious olfactory dysfunction (PIOD) receiving olfactory training. Study Design Retrospective cohort study. Methods This was a retrospective cohort study of patients with PIOD that received olfactory training. Adult patients with the major complaint of quantitative smell loss were recruited and treated at several ENT clinics in German between 2008 and 2018. The outcome was based on the association between smell‐loss related factors (including parosmia and phantosmia) and clinically relevant changes in overall and subdimension olfactory function of threshold, discrimination, and identification using binary logistic regression analysis. Results A total of 153 participants with PIOD were included. Clinically relevant improvements in overall olfactory function were more likely in those that had lower baseline olfactory function. Relevant improvements in discrimination function were more likely in those that had lower baseline olfactory function and those that had parosmia at the initial visit. Similarly, relevant improvements in odor identification were more likely in those that had a lower baseline olfactory function and in those who had parosmia at the first visit. Clinically significant improvements in odor threshold were more likely in those who were older in age. Conclusions This study demonstrated that the presence of parosmia is associated with clinically relevant recovery in olfactory discrimination and identification function in patients with PIOD receiving olfactory training. Level of Evidence 4 Laryngoscope, 131:618–623, 2021

Activation of cyclic nucleotide-gated channels is thought to involve two distinct steps: a recognition event in which a ligand binds to the channel and a conformational change that both opens the channel and increases the affinity of the channel for an agonist. Sequence similarity with the cyclic nucleotide-binding sites of cAMP-and cGMP-dependent protein kinases and the bacterial catabolite activating protein (CAP) suggests that the channel ligand binding site consists of a ␤-roll and three ␣-helices. Recent evidence has demonstrated that the third (or C) ␣-helix moves relative to the agonist upon channel activation, forming additional favorable contacts with the purine ring. Here we ask if channel activation also involves structural changes in the ␤-roll by investigating the contribution of a conserved arginine residue that, in CAP and the kinases, forms an important ionic interaction with the cyclized phosphate of the bound ligand. Mutations that conserve, neutralize, or reverse the charge on this arginine decreased the apparent affinity for ligand over four orders of magnitude but had little effect on the ability of bound ligand to open the channel. These data indicate that the cyclized phosphate of the nucleotide approaches to within 2-4 Å of the arginine, forming a favorable ionic bond that is largely unaltered upon activation. Thus, the binding site appears to be polarized into two distinct structural and functional domains: the ␤-roll stabilizes the ligand in a state-independent manner, whereas the C-helix selectively stabilizes the ligand in the open state of the channel. It is likely that these distinct contributions of the nucleotide/C-helix and nucleotide/␤-roll interactions may also be a general feature of the mechanism of activation of other cyclic nucleotide-binding proteins.Cyclic nucleotides regulate the activity of a diverse family of proteins involved in cellular signaling. These include a transcription factor (the bacterial catabolite activating protein, CAP), the cAMP-(PKA) 1 and cGMP-dependent protein kinases (PKG) and the cyclic nucleotide-gated (CNG) ion channels involved in visual and olfactory signal transduction (1, 2). Despite obvious divergence among the effector domains of these proteins, the cyclic nucleotide binding (CNB) sites appear to share a common architecture. Solution of the crystal structures of CAP (3) and a recombinant bovine PKA RI␣ subunit (4) has demonstrated that their CNB sites are formed from an ␣-helix (A helix), an 8-stranded ␤-roll, and two more ␣-helices (B and C), with the C-helix forming the back of the binding pocket. Six residues are invariant among all members of the CAP and kinase families: three glycines involved in turns between strands of the ␤-roll, an arginine and a glutamate, each of which contact the cyclic nucleotide, and an alanine whose function is uncertain (1) (see also Fig. 1). Strikingly, these six residues are conserved in the CNG channels. Thus, it has been suggested that the invariant residues play important and conserved roles in the fol...

Objectives The human sense of smell constitutes the main part of flavor perception. Typically, patients with loss of olfactory function complain of diminished perception during eating and drinking. However, some patients with smell loss still report normal enjoyment of foods. The aim of the present study was to compare orthonasal and retronasal olfactory function in patients with non‐sinonasal smell loss and subjectively normal flavor perception. Methods Nineteen patients (mean age [range] 52.0 [8–83 years]) with self‐reported olfactory impairment but subjective normal flavor perception were included. Olfactory performance was assessed using the Sniffin’ Sticks (TDI) for orthonasal and the Candy Smell Test (CST) for retronasal function. Visual analogue scales were used for self‐assessment of odor (SOP), taste (STP), and flavor perception (SFP), ranging from 0 (no perception) to 10 (excellent perception). Results Mean (SD) SFP was 8.0 (1.8). Mean (SD) orthonasal TDI‐score of all patients was 14.4 (5.3, range 6–25.3) with 11 patients classified as anosmic and eight as hyposmic. Mean/SD retronasal CST‐score was 8.8 (2.7, range 3–13) within the range of anosmia/hyposmia. No correlation was found between SFP and the CST (P = .62). Conclusion The present results showed that despite claiming normal flavor perception, our patients were ortho‐ and retronasally dysosmic using standard tests for olfactory function. Although other explanations could be possible, we suggest that this subjective flavor perception might be due to unconscious memory recall from previously experienced cross‐modal sensory interactions. Level of Evidence 4 Laryngoscope, 130:1629–1633, 2020