CRISPR-Cas9 In Vivo Gene Editing of KLKB1 for Hereditary Angioedema.

BACKGROUND: Hereditary angioedema is a rare genetic disease that leads to severe and unpredictable swelling attacks. NTLA-2002 is an in vivo gene-editing therapy based on clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9. NTLA-2002 targets the gene encoding kallikrein B1 (KLKB1), with the goal of lifelong control of angioedema attacks after a single dose. METHODS: In this phase 1 dose-escalation portion of a combined phase 1-2 trial of NTLA-2002 in adults with hereditary angioedema, we administered NTLA-2002 at a single dose of 25 mg, 50 mg, or 75 mg. The primary end points were the safety and side-effect profile of NTLA-2002 therapy. Secondary and exploratory end points included pharmacokinetics, pharmacodynamics, and clinical efficacy determined on the basis of investigator-confirmed angioedema attacks. RESULTS: Three patients received 25 mg of NTLA-2002, four received 50 mg, and three received 75 mg. At all dose levels, the most common adverse events were infusion-related reactions and fatigue. No dose-limiting toxic effects, serious adverse events, grade 3 or higher adverse events, or clinically important laboratory findings were observed after the administration of NTLA-2002. Dose-dependent reductions in the total plasma kallikrein protein level were observed between baseline and the latest assessment, with a mean percentage change of -67% in the 25-mg group, -84% in the 50-mg group, and -95% in the 75-mg group. The mean percentage change in the number of angioedema attacks per month between baseline and weeks 1 through 16 (primary observation period) was -91% in the 25-mg group, -97% in the 50-mg group, and -80% in the 75-mg group. Among all the patients, the mean percentage change in the number of angioedema attacks per month from baseline through the latest assessment was -95%. CONCLUSIONS: In this small study, a single dose of NTLA-2002 led to robust, dose-dependent, and durable reductions in total plasma kallikrein levels, and no severe adverse events were observed. In exploratory analyses, reductions in the number of angioedema attacks per month were observed at all dose levels. (Funded by Intellia Therapeutics; ClinicalTrials.gov number, NCT05120830.).

The importance of immunohistochemical analyses in evaluating the phenotype of Kv channel knockout mice.

To gain insights into the phenotype of voltage-gated potassium (Kv)1.1 and Kv4.2 knockout mice, we used immunohistochemistry to analyze the expression of component principal or α subunits and auxiliary subunits of neuronal Kv channels in knockout mouse brains. Genetic ablation of the Kv1.1 α subunit did not result in compensatory changes in the expression levels or subcellular distribution of related ion channel subunits in hippocampal medial perforant path and mossy fiber nerve terminals, where high levels of Kv1.1 are normally expressed. Genetic ablation of the Kv4.2 α subunit did not result in altered neuronal cytoarchitecture of the hippocampus. Although Kv4.2 knockout mice did not exhibit compensatory changes in the expression levels or subcellular distribution of the related Kv4.3 α subunit, we found dramatic decreases in the cellular and subcellular expression of specific Kv channel interacting proteins (KChIPs) that reflected their degree of association and colocalization with Kv4.2 in wild-type mouse and rat brains. These studies highlight the insights that can be gained by performing detailed immunohistochemical analyses of Kv channel knockout mouse brains.

Kv1.1 takes a deTOR from the axon to the dendrite.

In the October 6th issue of Science, Raab-Graham et al. described two surprising findings. They discovered that local dendritic translation of Kv1.1 occurs in CA1 dendrites of rat hippocampal slices and in cultured neurons. This local translation is inhibited by NMDA receptor-mediated synaptic signaling acting through the mTOR kinase.

Trafficking-dependent phosphorylation of Kv1.2 regulates voltage-gated potassium channel cell surface expression.

Kv1.2 alpha-subunits are components of low-threshold, rapidly activating voltage-gated potassium (Kv) channels in mammalian neurons. Expression and localization of Kv channels is regulated by trafficking signals encoded in their primary structure. Kv1.2 is unique in lacking strong trafficking signals and in exhibiting dramatic cell-specific differences in trafficking, which is suggestive of conditional trafficking signals. Here we show that a cluster of cytoplasmic C-terminal phosphorylation sites regulates Kv1.2 trafficking. Using tandem MS to analyze Kv1.2 purified from rat, human, and mouse brain, we identified in each sample in vivo phosphoserine (pS) phosphorylation sites at pS434, pS440, and pS441, as well as doubly phosphorylated pS440/pS441. We also found these sites, as well as pS449, on recombinant Kv1.2 expressed in heterologous cells. We found that phosphorylation at pS440/pS441 is present only on the post-endoplasmic reticulum (ER)/cell surface pool of Kv1.2 and is not detectable on newly synthesized and ER-localized Kv1.2, on which we did observe pS449 phosphorylation. Elimination of PS440/PS441 phosphorylation by mutation reduces cell-surface expression efficiency and functional expression of homomeric Kv1.2 channels. Interestingly, mutation of S449 reduces phosphorylation at pS440/pS441 and also decreases Kv1.2 cell-surface expression efficiency and functional expression. These mutations also suppress trafficking of Kv1.2/Kv1.4 heteromeric channels, suggesting that incorporation of Kv1.2 into heteromeric complexes confers conditional phosphorylation-dependent trafficking to diverse Kv channel complexes. These data support Kv1.2 phosphorylation at these clustered C-terminal sites as playing an important role in regulating trafficking of Kv1.2-containing Kv channels.

The orientation and molecular movement of a k(+) channel voltage-sensing domain.

Voltage-gated channels operate through the action of a voltage-sensing domain (membrane segments S1-S4) that controls the conformation of gates located in the pore domain (membrane segments S5-S6). Recent structural studies on the bacterial K(v)AP potassium channel have led to a new model of voltage sensing in which S4 lies in the lipid at the channel periphery and moves through the membrane as a unit with a portion of S3. Here we describe accessibility probing and disulfide scanning experiments aimed at determining how well the K(v)AP model describes the Drosophila Shaker potassium channel. We find that the S1-S3 helices have one end that is externally exposed, S3 does not undergo a transmembrane motion, and S4 lies in close apposition to the pore domain in the resting and activated state.

Neuroligin1: a cell adhesion molecule that recruits PSD-95 and NMDA receptors by distinct mechanisms during synaptogenesis.

BACKGROUND: The cell adhesion molecule pair neuroligin1 (Nlg1) and beta-neurexin (beta-NRX) is a powerful inducer of postsynaptic differentiation of glutamatergic synapses in vitro. Because Nlg1 induces accumulation of two essential components of the postsynaptic density (PSD) - PSD-95 and NMDA receptors (NMDARs) - and can physically bind PSD-95 and NMDARs at mature synapses, it has been proposed that Nlg1 recruits NMDARs to synapses through its interaction with PSD-95. However, PSD-95 and NMDARs are recruited to nascent synapses independently and it is not known if Nlg1 accumulates at synapses before these PSD proteins. Here, we investigate how a single type of cell adhesion molecule can recruit multiple types of synaptic proteins to new synapses with distinct mechanisms and time courses. RESULTS: Nlg1 was present in young cortical neurons in two distinct pools before synaptogenesis, diffuse and clustered. Time-lapse imaging revealed that the diffuse Nlg1 aggregated at, and the clustered Nlg1 moved to, sites of axodendritic contact with a rapid time course. Using a patching assay that artificially induced clusters of Nlg, the time course and mechanisms of recruitment of PSD-95 and NMDARs to those Nlg clusters were characterized. Patching Nlg induced clustering of PSD-95 via a slow palmitoylation-dependent step. In contrast, NMDARs directly associated with clusters of Nlg1 during trafficking. Nlg1 and NMDARs were highly colocalized in dendrites before synaptogenesis and they became enriched with a similar time course at synapses with age. Patching of Nlg1 dramatically decreased the mobility of NMDAR transport packets. Finally, Nlg1 was biochemically associated with NMDAR transport packets, presumably through binding of NMDARs to MAGUK proteins that, in turn, bind Nlg1. This interaction was essential for colocalization and co-transport of Nlg1 with NMDARs. CONCLUSION: Our results suggest that axodendritic contact leads to rapid accumulation of Nlg1, recruitment of NMDARs co-transported with Nlg1 soon thereafter, followed by a slower, independent recruitment of PSD-95 to those nascent synapses.

Structural consequences of Kcna1 gene deletion and transfer in the mouse hippocampus.

PURPOSE: Mice lacking the Kv1.1 potassium channel alpha subunit encoded by the Kcna1 gene develop recurrent behavioral seizures early in life. We examined the neuropathological consequences of seizure activity in the Kv1.1(-/-) (knock-out) mouse, and explored the effects of injecting a viral vector carrying the deleted Kcna1 gene into hippocampal neurons. METHODS: Morphological techniques were used to assess neuropathological patterns in hippocampus of Kv1.1(-/-) animals. Immunohistochemical and biochemical techniques were used to monitor ion channel expression in Kv1.1(-/-) brain. Both wild-type and knockout mice were injected (bilaterally into hippocampus) with an HSV1 amplicon vector that contained the rat Kcna1 subunit gene and/or the E. coli lacZ reporter gene. Vector-injected mice were examined to determine the extent of neuronal infection. RESULTS: Video/EEG monitoring confirmed interictal abnormalities and seizure occurrence in Kv1.1(-/-) mice. Neuropathological assessment suggested that hippocampal damage (silver stain) and reorganization (Timm stain) occurred only after animals had exhibited severe prolonged seizures (status epilepticus). Ablation of Kcna1 did not result in compensatory changes in expression levels of other related ion channel subunits. Vector injection resulted in infection primarily of granule cells in hippocampus, but the number of infected neurons was quite variable across subjects. Kcna1 immunocytochemistry showed "ectopic" Kv1.1 alpha channel subunit expression. CONCLUSIONS: Kcna1 deletion in mice results in a seizure disorder that resembles--electrographically and neuropathologically--the patterns seen in rodent models of temporal lobe epilepsy. HSV1 vector-mediated gene transfer into hippocampus yielded variable neuronal infection.

Guanidine hydrochloride can induce amyloid fibril formation from hen egg-white lysozyme.

The formation of amyloid fibrils is an intractable problem in which normally soluble protein polymerizes and forms insoluble ordered aggregates. Such aggregates can range from being a nuisance in vitro to being toxic in vivo. The latter is true for lysozyme, which has been shown to form toxic deposits in humans. In the present study, the effects of partial denaturation of hen egg-white lysozyme via incubation in a concentrated solution of the denaturant guanidine hydrochloride are investigated. Results show that when lysozyme is incubated under moderate guanidine hydrochloride concentrations (i.e., 2-5 M), where lysozyme is partially unfolded, fibrils form rapidly. Thioflavin T, Congo red, X-ray diffraction, transmission electron microscopy, atomic force microscopy, and circular dichroism spectroscopy are all used to verify the production of fibrils under these conditions. Incubation at very low or very high guanidine hydrochloride concentrations fails to produce fibrils. At very low denaturant concentrations, the structure of lysozyme is fully native and very stable. On the other hand, at very high denaturant concentrations, guanidine hydrochloride is capable of dissolving and dis-aggregating fibrils that are formed. Raising the temperature and/or concentration of lysozyme accelerates fibril formation by further adding to the concentration of partially unfolded species. The addition of preformed fibrils also accelerates fibril formation but only under partially unfolding conditions. The results presented here provide further evidence that partial unfolding is a prerequisite to fibril formation. Partial denaturation can accelerate fibril formation in much the same way that mutations have been shown to accelerate fibril formation.