A lysine residue from an extracellular turret switches the ion preference in a Cav3 T-Type channel from calcium to sodium ions

Cav3 T-type calcium channels from great pond snail Lymnaea stagnalis have a selectivity-filter ring of five acidic residues, EE(D)DD. Splice variants with exons 12b or 12a spanning the extracellular loop between the outer helix IIS5 and membrane-descending pore helix IIP1 (IIS5-P1) in Domain II of the pore module possess calcium selectivity or dominant sodium permeability, respectively. Here, we use AlphaFold2 neural network software to predict that a lysine residue in exon 12a is salt-bridged to the aspartate residue immediately C terminal to the second-domain glutamate in the selectivity filter. Exon 12b has a similar folding but with an alanine residue in place of lysine in exon 12a. We express LCav3 channels with mutated exons Ala-12b-Lys and Lys-12a-Ala and demonstrate that they switch the ion preference to high sodium permeability and calcium selectivity, respectively. We propose that in the calcium-selective variants, a calcium ion chelated between Domain II selectivity-filter glutamate and aspartate is knocked-out by the incoming calcium ion in the process of calcium permeation, whereas sodium ions are repelled. The aspartate is neutralized by the lysine residue in the sodium-permeant variants, allowing for sodium permeation through the selectivity-filter ring of four negatively charged residues akin to the prokaryotic sodium channels with four glutamates in the selectivity filter. The evolutionary adaptation in invertebrate LCav3 channels highlight the involvement of a key, ubiquitous aspartate, "a calcium beacon" of sorts in the outer pore of Domain II, as determinative for the calcium ion preference over sodium ions through eukaryotic Cav1, Cav2, and Cav3 channels.

Construct Validity of the EuroQoL-5 Dimension and the Health Utilities Index in Head and Neck Cancer

Objective

The objective of this study was to evaluate the construct validity of 2 health utility instruments—the EuroQoL–5 Dimension (EQ-5D) and the Health Utilities Index–Mark 3 (HUI-3)—and to compare them with disease-specific measures in patients with head and neck cancer.

Study Design

Prospective cross-sectional analysis.

Setting

Princess Margaret Cancer Centre.

Methods

Patients were administered the EQ-5D, HUI-3, the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) and its head and neck cancer module (EORTC QLQ-H&N35), and the University of Washington Quality of Life Questionnaire (UWQoL). Several a priori expected relations were examined. The correlative and discriminative properties of the various instruments were examined.

Results

A total of 209 patients completed the 4 questionnaires. A significant ceiling effect was observed among EQ-5D responses (23% reported a maximum score of 1). The EQ-5D (rho = 0.79) and HUI-3 (rho = 0.60) had a strong correlation with the social-emotional domain of the UWQoL. The EQ-5D had a moderate correlation with the physical domain of the UWQoL (rho = 0.42), whereas the HUI-3 had a weak correlation (rho = 0.29). The EQ-5D and HUI-3 were able to distinguish among levels of health severity measured on the EORTC QLQ-C30 though not the QLQ-H&N35. Comparatively, the UWQoL was able to distinguish levels of disease severity on the EORTC QLQ-C30 and QLQ-H&N35.

Conclusion

The results of this study demonstrate that disease-specific domains from head and neck quality-of-life instruments are not strongly correlated with the EQ-5D and HUI-3. Consideration should be put toward development of a disease-specific preference-based measure for health economic evaluation.

Level of evidence

4.

Unique cysteine-enriched, D2L5 and D4L6 extracellular loops in CaV3 T-type channels alter the passage and block of monovalent and divalent ions

Invertebrate LCa_V3 shares the quintessential features of vertebrate Ca_V3 T-type channels, with a low threshold of channel activation, rapid activation and inactivation kinetics and slow deactivation kinetics compared to other known Ca²⁺ channels, the Ca_V1 and Ca_V2 channels. Unlike the vertebrates though, Ca_V3 T-type channels in non-cnidarian invertebrates possess an alternative exon 12 spanning the D2L5 extracellular loop, which alters the invertebrate LCa_V3 channel into a higher Na⁺ and lower Ca²⁺ current passing channel, more resembling a classical Na_V1 Na⁺ channel. Cnidarian Ca_V3 T-type channels can possess genes with alternative cysteine-rich, D4L6 extracellular loops in a manner reminiscent of the alternative cysteine-rich, D2L5 extracellular loops of non-cnidarian invertebrates. We illustrate here that the preferences for greater Na⁺ or Ca²⁺ ion current passing through Ca_V3 T-type channels are contributed by paired cysteines within D2L5 and D4L6 extracellular loops looming above the pore selectivity filter. Swapping of invertebrate tri- and tetra-cysteine containing extracellular loops, generates higher Na⁺ current passing channels in human Ca_V3.2 channels, while corresponding mono- and di-cysteine loop pairs in human Ca_V3.2 generates greater Ca²⁺ current passing, invertebrate LCa_V3 channels. Alanine substitutions of unique D2L5 loop cysteines of LCa_V3 channels increases relative monovalent ion current sizes and increases the potency of Zn²⁺ and Ni²⁺ block by ~ 50× and ~ 10× in loop cysteine mutated channels respectively, acquiring characteristics of the high affinity block of Ca_V3.2 channels, including the loss of the slowing of inactivation kinetics during Zn²⁺ block. Charge neutralization of a ubiquitous aspartate residue of calcium passing Ca_V1, Ca_V2 and Ca_V3 channels, in the outer pore of the selectivity filter residues in Domain II generates higher Na⁺ current passing channels in a manner that may resemble how the unique D2L5 extracellular loops of invertebrate Ca_V3 channels may confer a relatively higher peak current size for Na⁺ ions over Ca²⁺ The extracellular loops of Ca_V3 channels are not engaged with accessory subunit binding, as the other Na⁺ (Na_V1) and Ca²⁺ (Ca_V1/Ca_V2) channels, enabling diversity and expansion of cysteine-bonded extracellular loops, which appears to serve, amongst other possibilities, to alter to the preferences for passage of Ca²⁺ or Na⁺ ions through invertebrate Ca_V3 channels.

Phase II Trial of Pure Hypofractionated Radiotherapy in the Treatment of Localized Carcinoma of the Prostate

Purpose To evaluate acute and late genitourinary (GU) and gastrointestinal (GI) toxicity and the biochemical control of pure hypofractionated radiotherapy (without acceleration) for the treatment of prostate cancer. Methods and materials This phase II prospective trial evaluated low-risk and intermediate-risk prostate cancer patients who received hypofractionated radiotherapy. Fifty-three patients with low-risk prostate cancer received 50 Gy in 15 fractions, 156 patients with intermediate-risk prostate cancer received 60 Gy in 20 fractions over eight weeks. Acute toxicity and late toxicity were graded per the Radiation Therapy Oncology Group (RTOG) toxicity scales and the Phoenix Definition (nadir plus two) defined biochemical failure. Results Median follow-up was 6.5 years. Acute phase grade 2/3 toxicity was 6%/0 and 8%/2% for GI and GU symptoms, respectively, and one grade 4 acute GU toxicity (0.5%). Late grade 2/3 GI and GU toxicity were 7%/0 and 8%/0.5%, respectively. There were no late grade 4 toxicities. The five-year freedom-from-biochemical-failure (FFBF) rates were 85% for low-risk patients and 80% for intermediate-risk patients. Conclusions Pure hypofractionation seems to be associated with low toxicity rates and biochemical control rates that are similar or better than those observed with accelerated hypofractionated or conventionally fractionated therapy.

Calmodulin regulates Cav3 T-type channels at their gating brake

Calcium (Cav1 and Cav2) and sodium channels possess homologous CaM-binding motifs, known as IQ motifs in their C termini, which associate with calmodulin (CaM), a universal calcium sensor. Cav3 T-type channels, which serve as pacemakers of the mammalian brain and heart, lack a C-terminal IQ motif. We illustrate that T-type channels associate with CaM using co-immunoprecipitation experiments and single particle cryo-electron microscopy. We demonstrate that protostome invertebrate (LCav3) and human Cav3.1, Cav3.2, and Cav3.3 T-type channels specifically associate with CaM at helix 2 of the gating brake in the I-II linker of the channels. Isothermal titration calorimetry results revealed that the gating brake and CaM bind each other with high-nanomolar affinity. We show that the gating brake assumes a helical conformation upon binding CaM, with associated conformational changes to both CaM lobes as indicated by amide chemical shifts of the amino acids of CaM in 1H-15N HSQC NMR spectra. Intact Ca2+-binding sites on CaM and an intact gating brake sequence (first 39 amino acids of the I-II linker) were required in Cav3.2 channels to prevent the runaway gating phenotype, a hyperpolarizing shift in voltage sensitivities and faster gating kinetics. We conclude that the presence of high-nanomolar affinity binding sites for CaM at its universal gating brake and its unique form of regulation via the tuning of the voltage range of activity could influence the participation of Cav3 T-type channels in heart and brain rhythms. Our findings may have implications for arrhythmia disorders arising from mutations in the gating brake or CaM.

Selectivity filters and cysteine-rich extracellular loops in voltage-gated sodium, calcium, and NALCN channels

How nature discriminates sodium from calcium ions in eukaryotic channels has been difficult to resolve because they contain four homologous, but markedly different repeat domains. We glean clues from analyzing the changing pore region in sodium, calcium and NALCN channels, from single-cell eukaryotes to mammals. Alternative splicing in invertebrate homologs provides insights into different structural features underlying calcium and sodium selectivity. NALCN generates alternative ion selectivity with splicing that changes the high field strength (HFS) site at the narrowest level of the hourglass shaped pore where the selectivity filter is located. Alternative splicing creates NALCN isoforms, in which the HFS site has a ring of glutamates contributed by all four repeat domains (EEEE), or three glutamates and a lysine residue in the third (EEKE) or second (EKEE) position. Alternative splicing provides sodium and/or calcium selectivity in T-type channels with extracellular loops between S5 and P-helices (S5P) of different lengths that contain three or five cysteines. All eukaryotic channels have a set of eight core cysteines in extracellular regions, but the T-type channels have an infusion of 4–12 extra cysteines in extracellular regions. The pattern of conservation suggests a possible pairing of long loops in Domains I and III, which are bridged with core cysteines in NALCN, Cav, and Nav channels, and pairing of shorter loops in Domains II and IV in T-type channel through disulfide bonds involving T-type specific cysteines. Extracellular turrets of increasing lengths in potassium channels (Kir2.2, hERG, and K2P1) contribute to a changing landscape above the pore selectivity filter that can limit drug access and serve as an ion pre-filter before ions reach the pore selectivity filter below. Pairing of extended loops likely contributes to the large extracellular appendage as seen in single particle electron cryo-microscopy images of the eel Na_v1 channel.

Progressive enlargement of a circumscribed choroidal hemangioma. A clinicopathologic correlation

A man with a circumscribed choroidal hemangioma was followed up for almost 10 years as the tumor showed gradual, progressive enlargement in both diameter and thickness. In spite of photocoagulation therapy, a total retinal detachment and blindness ensued. Enucleation was performed because the possibility of amelanotic choroidal melanoma could not be absolutely excluded. Although the tumor thickness measured by ultrasonography before enucleation was 4.5 mm, the lesion measured only 2.0 mm in thickness in the pathology laboratory. Circumscribed choroidal hemangioma rarely demonstrates clinical evidence of growth. It appears that the tumor enlargement noted in this case was due to venous congestion in the tumor and not to cell multiplication.

An alternative technique of local anesthesia for vitreoretinal surgery

Retrobulbar anesthesia produces effective local anesthesia for ocular surgery, but significant complications have been reported with its use. To maintain its efficacy and to minimize the risks associated with the passage of a needle behind the eye, we have placed local anesthesia into sub-Tenon's space posteriorly using a blunt irrigating cannula in 100 patients undergoing vitreous or retinal procedures. Posterior Tenon's capsule is opened by blunt dissection, allowing the irrigating cannula to be passed into the posterior sub-Tenon's space for anesthetic injection. The technique was effective in 98 of 100 patients, and no morbidity was associated with its use.

Laser treatment of subfoveolar choroidal neovascular membranes

We prospectively studied the safety and efficacy of subfoveolar laser treatment of choroidal neovascular membranes (CNVM) in 29 eyes. With one to four treatments, all CNVMs were successfully eradicated. Central visual acuity improved in 31% and stabilized in 69%. Vision did not deteriorate in any of the eyes. In appropriately selected eyes, subfoveolar treatment appears safe and effective in halting the exudative response and minimizing scotoma size, thus facilitating the use of low-vision aids.

Visual improvement after four laser treatments to foveola for choroidal neovascular membrane

With the advent of new laser technology and refined treatment techniques, it is possible that visual morbidity may be reduced by the treatment of subfoveolar choroidal neovascular membranes. This case report from our prospective study series describes an eye that required four monochromatic green subfoveolar treatments for an active choroidal neovascular membrane, which was ultimately eradicated. Even though the foveola was treated four times, the visual acuity improved from 20/200 preoperatively to 20/40 postoperatively. This case demonstrates that in carefully selected cases, even with multiple subfoveolar treatments, central visual acuity not only can be preserved, but also can actually be improved.

Response competition and target word detection during shadowing in a dichotic listening task

College students (N = 24) served as subjects in a within-subjects study of auditory attention in which four tasks were performed. In the easiest task, a single passage was presented and shadowed while target word detections were indicated by pressing a key. The other three tasks also required target word detection, but a second passage was presented simultaneously. One task had no target words in the unshadowed passage; the other two tasks required a key-pressing response to the target words in both passages, either with one hand or with each hand. We expected performance to decrease as task complexity increased; this was partially confirmed. The task of shadowing and detecting target words is too difficult to be used to test perception or response limitations of attention.

Peripheral circumferential retinal scatter photocoagulation for the treatment of proliferative sickle retinopathy. An update

Forty-four patients (70 eyes, 220 sea fans) with proliferative sickle retinopathy (PSR) received peripheral circumferential retinal scatter photocoagulation (PCRP) to the peripheral zones of retinal capillary nonperfusion. With an average follow-up of 3.3 years, 33% of preexisting sea fans regressed completely, 46% regressed partially, 19% remained stable, and 2% showed progression. De novo neovascularization developed after treatment in only one eye (1.4%). Ninety-five percent of patients treated had a final visual acuity of 20/30 or better and only one patient (2%) developed a nonresolving vitreous hemorrhage requiring vitrectomy surgery. These results confirm the authors' previous report and continue to compare favorably to the natural history of PSR in which de novo lesions developed in 58%, and 12% of eyes ended with a visual acuity of 20/200 or less. PCRP seems preferable to other techniques in reducing the risk of nonresolving vitreous hemorrhage and/or traction retinal detachment, although randomized controlled studies are needed to conclusively assess the safety and efficacy of this strategy in treating PSR.

Peripheral circumferential retinal scatter photocoagulation for treatment of proliferative sickle retinopathy

Twenty-nine patients (40 eyes) with proliferative sickle retinopathy (PSR) were treated with circumferential argon laser scatter photocoagulation to zones of peripheral retinal capillary nonperfusion. Each eye was examined in a prospective fashion, with a mean follow-up of 1.4 years. Following scatter treatment, 26% of the pre-existing sea fans regressed completely, 57% regressed partially, 17% remained stable, and none showed progression. In only one eye did de novo neovascularization develop. The results compare favorably with the natural history of PSR (Condon et al, 1980), in which de novo lesions occurred in 58%, and the visual acuity was decreased to less than 20/200 in 12% of affected eyes. Severe iatrogenic complications reported following direct focal treatment of sea fans, such as vitreous hemorrhage, progressive traction retinal detachment, retinal breaks, and choroidal-retinal-vitreal neovascularization were virtually eliminated.

Metastatic renal cell carcinoma to the eye and adnexae: a report of three cases and review of the literature

Three cases of metastatic renal cell carcinoma to the ocular structures are presented. Each of these tumors clinically simulated a more common ocular entity, thus causing diagnostic difficulty. The first patient had a metastatic tumor to the eyelid that clinically simulated a large chalazion. The second patient had a choroidal tumor with clinical features and ancillary studies strongly suggestive of a primary choroidal melanoma. The third patient presented with unilateral proptosis secondary to an orbital mass that was clinically believed to be a cavernous hemangioma of the orbit. In each case, there was a long interval between the ocular metastasis, which represented the first sign of metastatic disease.

The differential diagnosis of posterior uveal melanoma

Two large studies from the Armed Forces Institute of Pathology (AFIP) have listed the various lesions which may clinically resemble malignant melanomas of the posterior uvea (pseudomelanomas). The studies from the AFIP were based upon histologic examination of eyes which were enucleated. The present study reports on 400 consecutive patients who were referred but who proved, by clinical evaluation, rather than by enucleation, to have a pseudomelanoma. Although about 40 different conditions were found to simulate melanoma, the more commonly encountered ones included suspicious choroidal nevus (26.5%), disciform degeneration (12.5%), peripheral disciform degeneration (11%), congenital hypertrophy of the retinal pigment epithelium (9.5%), and choroidal hemangioma (8%). The authors believe that this series provides the clinician with a differential diagnosis for posterior uveal melanomas which accurately reflects the clinical problem confronting ophthalmologists today.

Diagnosis and management of cancer metastatic to the uvea: a study of 70 cases

Although metastatic cancer to the uvea is reported to be the most common intraocular malignancy, most ophthalmologists have had little experience with its diagnosis and treatment. This report describes our experience with the diagnosis and management of 70 patients with metastatic cancer to the uvea. Many patients were evaluated with modern diagnostic modalities such as fluorescein angiography, ultrasonography, and the 32P test when indicated. Thirty-one percent of patients had no history of previous malignancy, and the ocular complaints represented the first symptoms of systemic cancer. The ocular malignancy often simulated better-known ophthalmic entities, and the referring diagnosis was correct in only 38% of cases. This series, therefore, reflects the clinical problem confronting the practicing ophthalmologist. About one-half of the patients were treated with external beam irradiation to the involved eye(s), which often resulted in dramatic resolution of the tumor and visual return. Other patients had either no treatment, chemotherapy, or enucleation in selected instances.