Safety, Tolerability, and Pharmacokinetics of an Oral Small Molecule Inhibitor of IL-17A (LY3509754): A Phase I Randomized Placebo-Controlled Study.

For some patients with psoriasis, orally administered small molecule inhibitors of interleukin (IL)-17A may represent a convenient alternative to IL-17A-targeting monoclonal antibodies. This first-in-human study assessed the safety, tolerability, pharmacokinetics (PKs), and peripherally circulating IL-17A target engagement profile of single or multiple oral doses of the small molecule IL-17A inhibitor LY3509754 (NCT04586920). Healthy participants were randomly assigned to receive LY3509754 or placebo in sequential escalating single ascending dose (SAD; dose range 10-2,000 mg) or multiple ascending dose (MAD; dose range 100-1,000 mg daily for 14 days) cohorts. The study enrolled 91 participants (SAD, N = 51 and MAD, N = 40) aged 21-65 years (71% men). LY3509754 had a time to maximum concentration (Tmax) of 1.5-3.5 hours, terminal half-life of 11.4-19.1 hours, and exhibited dose-dependent increases in exposure. LY3509754 had strong target engagement, indicated by elevated plasma IL-17A levels within 12 hours of dosing. Four participants from the 400-mg (n = 1) and 1,000-mg (n = 3) MAD cohorts experienced increased liver transaminases or acute hepatitis (onset ≥ 12 days post-last LY3509754 dose), consistent with drug-induced liver injury (DILI). One case of acute hepatitis was severe, resulted in temporary hospitalization, and was classified as a serious adverse event. No adverse effects on other major organ systems were observed. Liver biopsies from three of the four participants revealed lymphocyte-rich, moderate-to-severe lobular inflammation. We theorize that the DILI relates to an off-target effect rather than IL-17A inhibition. In conclusion, despite strong target engagement and a PK profile that supported once-daily administration, this study showed that oral dosing with LY3509754 was poorly tolerated.

Safety and Tolerability of Sarecycline for the Treatment of Acne Vulgaris: Results from a Phase III, Multicenter, Open-Label Study and a Phase I Phototoxicity Study.

Objective: We sought to evaluate the safety, tolerability, and patterns of use for the once-daily oral, narrow-spectrum antibiotic sarecycline in patients with moderate-to-severe acne vulgaris during a 40-week Phase III, multicenter, open-label extension study. Participants: Patients aged nine years or older with moderate-to-severe acne who completed one of two prior Phase III, double-blind, placebo-controlled, 12-week trials in which they received sarecycline 1.5mg/kg/day or placebo were included. Measurements: The primary assessment was the safety of sarecycline 1.5mg/kg/day for 40 weeks as indicated by adverse events (AEs), vital signs, electrocardiograms, clinical laboratory tests, and physical examinations. Patterns of sarecycline use were a secondary assessment. Results: The safety population included 483 patients; 354 patients (73.3%) completed the study. The most common reasons for premature discontinuation were withdrawal by the patient (14.5%), lost to follow-up (7.9%), and AEs (2.5%). The most common treatment-emergent AEs (TEAEs) were nasopharyngitis (3.7%), upper-respiratory-tract infection (3.3%), headache (2.9%), and nausea (2.1%). Clinical laboratory evaluations suggested no clinically meaningful differences between the treatment sequences. Rates of TEAEs commonly associated with other tetracycline antibiotics include dizziness (0.4%) and sunburn (0.2%), and for gastrointestinal TEAEs, nausea (2.1%), vomiting (1.9%), and diarrhea (1.0%). Also reported herein are the results of a Phase I phototoxicity study. Conclusion: Patients aged nine years or older with moderate-to-severe acne vulgaris who received sarecycline once daily for up to 40 weeks showed low rates of TEAEs, with nasopharyngitis, upper-respiratory-tract infection, headache, and nausea being the only TEAEs reported by 2% or more of patients. No clinically meaningful safety findings were noted. ClinicalTrials.gov Registration: NCT02413346.

Once-Daily Oral Sarecycline 1.5 mg/kg/day Is Effective for Moderate to Severe Acne Vulgaris: Results from Two Identically Designed, Phase 3, Randomized, Double-Blind Clinical Trials.

BACKGROUND: Side effects may limit the use of current tetracycline-class antibiotics for acne. OBJECTIVE: Evaluate the efficacy and safety of once-daily sarecycline, a novel, narrow-spectrum tetracycline-class antibiotic, in moderate to severe acne. METHODS: Patients 9-45 years with moderate to severe facial acne (Investigator's Global Assessment [IGA] score ≥ 3, 20-50 inflammatory and ≤ 100 noninflammatory lesions, and ≤ 2 nodules) were randomized 1:1 to sarecycline 1.5 mg/kg/day or placebo for 12 weeks in identically designed phase 3 studies (SC1401 and SC1402). RESULTS: In SC1401 (sarecycline n=483, placebo n=485) and SC1402 (sarecycline n=519, placebo n=515), at week 12, IGA success (≥ 2-grade improvement and score 0 [clear] or 1 [almost clear]) rates were 21.9% and 22.6% (sarecycline), respectively, versus 10.5% and 15.3% (placebo; P less than 0.0001 and P equals 0.0038). Onset of efficacy in inflammatory lesions occurred by the first visit (week 3), with mean percentage reduction in inflammatory lesions at week 12 in SC1401 and SC1402 of -51.8% and -49.9% (sarecycline), respectively, versus -35.1% and -35.4% (placebo; P less than 0.0001). Onset of efficacy for absolute reduction of noninflammatory lesion count occurred at week 6 in SC1401 (P less than 0.05) and week 9 in SC1402 (P less than 0.01). In SC1401, the most common TEAEs (in ≥ 2% of either sarecycline or placebo group) were nausea (4.6% [sarecycline]; 2.5% [placebo]), nasopharyngitis (3.1%; 1.7%), headache (2.7%; 2.7%), and vomiting (2.1%; 1.4%) and, in SC1402, nasopharyngitis (2.5%; 2.9%) and headache (2.9%; 4.9%). Most were not considered treatment-related. Vestibular (dizziness, tinnitus, vertigo) and phototoxic (sunburn, photosensitivity) TEAEs both occurred in ≤ 1% of sarecycline patients. Gastrointestinal TEAE rates for sarecycline were low. Among females, vulvovaginal candidiasis (SC1401: 1.1% [sarecycline] and 0 [placebo]; SC1402: 0.3% and 0) and mycotic infection (0.7% and 0; 1.0% and 0) rates were low. CONCLUSION: The narrow-spectrum antibiotic sarecycline was safe, well tolerated, and effective for moderate to severe acne, with low rates of side effects common with tetracycline antibiotics. J Drugs Dermatol. 2018;17(9):987-996.

The channel-kinase TRPM7 regulates antigen gathering and internalization in B cells.

Members of the transient receptor potential (TRP) family of ion channels are cellular sensors involved in numerous physiological and pathological processes. We identified the TRP subfamily M member 7 (TRPM7) channel-kinase as a previously uncharacterized regulator of B cell activation. We showed that TRPM7 played a critical role in the early events of B cell activation through both its ion channel and kinase functions. DT40 B cells deficient in TRPM7 or expressing a kinase-deficient mutant of TRPM7 showed defective gathering of antigen and prolonged B cell receptor (BCR) signaling. We showed that lipid metabolism was altered in TRPM7-deficient cells and in cells expressing a kinase-deficient mutant of TRPM7 and suggest that PLC-γ2 may be a target of the kinase activity of TRPM7. Primary B cells that expressed less TRPM7 or were treated with a pharmacological inhibitor of TRPM7 also displayed defective antigen gathering and increased BCR signaling. Finally, we demonstrated that blocking TRPM7 function compromised antigen internalization and presentation to T cells. These data suggest that TRPM7 controls an essential process required for B cell affinity maturation and the production of high-affinity antibodies.

The TRPM7 kinase limits receptor-induced calcium release by regulating heterotrimeric G-proteins.

The melastatin-related transient receptor potential member 7 (TRPM7) is a unique fusion protein with both ion channel function and enzymatic α-kinase activity. TRPM7 is essential for cellular systemic magnesium homeostasis and early embryogenesis; it promotes calcium transport during global brain ischemia and emerges as a key player in cancer growth. TRPM7 channels are negatively regulated through G-protein-coupled receptor-stimulation, either by reducing cellular cyclic adenosine monophosphate (cAMP) or depleting phosphatidylinositol bisphosphate (PIP2) levels in the plasma membrane. We here identify that heterologous overexpression of human TRPM7-K1648R mutant will lead to disruption of protease or purinergic receptor-induced calcium release. The disruption occurs at the level of Gq, which requires intact TRPM7 kinase phosphorylation activity for orderly downstream signal transduction to activate phospholipase (PLC)ß and cause calcium release. We propose that this mechanism may support limiting GPCR-mediated calcium signaling in times of insufficient cellular ATP supply.

The TRPM2 ion channel contributes to cytokine hyperproduction in a mouse model of Down Syndrome.

Trisomy 21 (Down Syndrome, DS) is the most common chromosomal anomaly. Although DS is mostly perceived as affecting cognitive abilities and cardiac health, individuals with DS also exhibit dysregulated immune functions. Levels of pro-inflammatory cytokines are increased, but intrinsic alterations of innate immunity are understudied in DS. Furthermore, elevated Reactive Oxygen Species (ROS) are well documented in individuals with DS, further exacerbating inflammatory processes. Chronic inflammation and oxidative stress are often precursors of subsequent tissue destruction and pathologies, which affect a majority of persons with DS. Together with ROS, the second messenger ion Ca2+ plays a central role in immune regulation. TRPM2 (Transient Receptor Potential Melastatin 2) is a Ca2+-permeable ion channel that is activated under conditions of oxidative stress. The Trpm2 gene is located on human Chromosome 21 (Hsa21). TRPM2 is strongly represented in innate immune cells, and numerous studies have documented its role in modulating inflammation. We have previously found that as a result of suboptimal cytokine production, TRPM2-/- mice are highly susceptible to the bacterial pathogen Listeria monocytogenes (Lm). We therefore used Lm infection to trigger and characterize immune responsiveness in the DS mouse model Dp10(yey), and to investigate the potential contribution of TRPM2. In comparison to wildtype (WT), Dp10(yey) mice show an increased resistance against Lm infection and higher IFNγ serum concentrations. Using a gene elimination approach, we show that these effects correlate with Trpm2 gene copy number, supporting the notion that Trpm2 might promote hyperinflammation in DS.

TRPM7 Kinase Controls Calcium Responses in Arterial Thrombosis and Stroke in Mice.

OBJECTIVE: TRPM7 (transient receptor potential cation channel, subfamily M, member 7) is a ubiquitously expressed bifunctional protein comprising a transient receptor potential channel segment linked to a cytosolic α-type serine/threonine protein kinase domain. TRPM7 forms a constitutively active Mg2+ and Ca2+ permeable channel, which regulates diverse cellular processes in both healthy and diseased conditions, but the physiological role of TRPM7 kinase remains largely unknown. APPROACH AND RESULTS: Here we show that point mutation in TRPM7 kinase domain deleting the kinase activity in mice (Trpm7R/R ) causes a marked signaling defect in platelets. Trpm7R/R platelets showed an impaired PIP2 (phosphatidylinositol-4,5-bisphosphate) metabolism and consequently reduced Ca2+ mobilization in response to stimulation of the major platelet receptors GPVI (glycoprotein VI), CLEC-2 (C-type lectin-like receptor), and PAR (protease-activated receptor). Altered phosphorylation of Syk (spleen tyrosine kinase) and phospholipase C γ2 and ß3 accounted for these global platelet activation defects. In addition, direct activation of STIM1 (stromal interaction molecule 1) with thapsigargin revealed a defective store-operated Ca2+ entry mechanism in the mutant platelets. These defects translated into an impaired platelet aggregate formation under flow and protection of the mice from arterial thrombosis and ischemic stroke in vivo. CONCLUSIONS: Our results identify TRPM7 kinase as a key modulator of phospholipase C signaling and store-operated Ca2+ entry in platelets. The protection of Trpm7R/R mice from acute ischemic disease without developing intracranial hemorrhage indicates that TRPM7 kinase might be a promising antithrombotic target.

Cigarette smoke inhibits LPS-induced FABP5 expression by preventing c-Jun binding to the FABP5 promoter.

Cigarette smoking is the primary cause of chronic obstructive pulmonary disease (COPD) with repeated and sustained infections linked to disease pathogenesis and exacerbations. The airway epithelium constitutes the first line of host defense against infection and is known to be impaired in COPD. We have previously identified Fatty Acid Binding Protein 5 (FABP5) as an important anti-inflammatory player during respiratory infections and showed that overexpression of FABP5 in primary airway epithelial cells protects against bacterial infection and inflammation. While cigarette smoke down regulates FABP5 expression, its mechanism remains unknown. In this report, we have identified three putative c-Jun binding sites on the FABP5 promoter and show that cigarette smoke inhibits the binding of c-Jun to its consensus sequence and prevents LPS-induced FABP5 expression. Using chromatin immunoprecipitation, we have determined that c-Jun binds the FABP5 promoter when stimulated with LPS but the presence of cigarette smoke greatly reduces this binding. Furthermore, cigarette smoke or a mutation in the c-Jun binding site inhibits LPS-induced FABP5 promoter activity. These data demonstrate that cigarette smoke interferes with FABP5 expression in response to bacterial infection. Thus, functional activation of FABP5 may be a new therapeutic strategy when treating COPD patients suffering from exacerbations.

Signature Channels of Excitability no More: L-Type Channels in Immune Cells.

Although the concept of Ca(2+) as a universal messenger is well established, it was assumed that the regulatory mechanisms of Ca(2+)-signaling were divided along the line of electric excitability. Recent advances in molecular biology and genomics have, however, provided evidence that non-excitable cells such as immunocytes also express a wide and diverse pool of ion channels that does not differ as significantly from that of excitable cells as originally assumed. Ion channels and transporters are involved in virtually all aspects of immune response regulation, from cell differentiation and development to activation, and effector functions such as migration, antibody-secretion, phagosomal maturation, or vesicular delivery of bactericidal agents. This comprises TRP channel family members, voltage- and Ca(2+)-gated K(+)- and Na(+)-channels, as well as unexpectedly, components of the CaV1-subfamily of voltage-gated L-type Ca(2+)-channels, originally thought to be signature molecules of excitability. This article provides an overview of recent observations made in the field of CaV1 L-type channel function in the immune context, as well as presents results we obtained studying these channels in B-lymphocytes.

TRPM6 kinase activity regulates TRPM7 trafficking and inhibits cellular growth under hypomagnesic conditions.

The channel kinases TRPM6 and TRPM7 are both members of the melastatin-related transient receptor potential (TRPM) subfamily of ion channels and the only known fusions of an ion channel pore with a kinase domain. TRPM6 and TRPM7 form functional, tetrameric channel complexes at the plasma membrane by heteromerization. TRPM6 was previously shown to cross-phosphorylate TRPM7 on threonine residues, but not vice versa. Genetic studies demonstrated that TRPM6 and TRPM7 fulfill non-redundant functions and that each channel contributes uniquely to the regulation of Mg(2+) homeostasis. Although there are indications that TRPM6 and TRPM7 can influence each other's cellular distribution and activity, little is known about the functional relationship between these two channel-kinases. In the present study, we examined how TRPM6 kinase activity influences TRPM7 serine phosphorylation, intracellular trafficking, and cell surface expression of TRPM7, as well as Mg(2+)-dependent cellular growth. We found TRPM7 serine phosphorylation via the TRPM6 kinase, but no TRPM6 serine phosphorylation via the TRPM7 kinase. Intracellular trafficking of TRPM7 was altered in HEK-293 epithelial kidney cells and DT40 B cells in the presence of TRPM6 with intact kinase activity, independently of the availability of extracellular Mg(2+), but TRPM6/7 surface labeling experiments indicate comparable levels of the TRPM6/7 channels at the plasma membrane. Furthermore, using a complementation approach in TRPM7-deficient DT40 B-cells, we demonstrated that wild-type TRPM6 inhibited cell growth under hypomagnesic cell culture conditions in cells co-expressing TRPM6 and TRPM7; however, co-expression of a TRPM6 kinase dead mutant had no effect-a similar phenotype was also observed in TRPM6/7 co-expressing HEK-293 cells. Our results provide first clues about how heteromer formation between TRPM6 and TRPM7 influences the biological activity of these ion channels. We show that TRPM6 regulates TRPM7 intracellular trafficking and TRPM7-dependent cell growth. All these effects are dependent upon the presence of an active TRPM6 kinase domain. Dysregulated Mg(2+)-homeostasis causes or exacerbates many pathologies. As TRPM6 and TRPM7 are expressed simultaneously in numerous cell types, understanding how their relationship impacts regulation of Mg(2+)-uptake is thus important knowledge.

The channel-kinase TRPM7, revealing the untold story of Mg(2+) in cellular signaling.

Ion homeostasis dysregulations have severe effects on human health, impairing the effectiveness and appropriateness of major cellular events, including immune responses. The adverse effects of Mg(2+) deficiency on cellular physiology are well known and documented, but mechanistic insights into Mg(2+) sensitive signal transduction are still lacking. TRPM7 and its sister channel TRPM6 stand out as the only known fusions of an ion pore with a Ser/Thr kinase domain. Both channels are permeable to divalent cations and are central regulators of Mg(2+) homeostasis. One crucial aspect of TRPM7 function we have extensively studied is the relationship between its ion channel portion and its C-terminal Ser/Thr kinase domain. The modulation of ion channels by phosphorylation through exogenous kinases is common, however the covalent bound between the TRPM7 channel and its kinase suggests a novel kind of link between ion-entry and signal transduction events. Current knowledge supports a reciprocal "two-way street" model where TRPM7-kinase modulates ion transport function through Ser/Thr phosphorylation, and in turn, channel gating and ionic conditions in close proximity to the pore regulate TRPM7-kinase mediated signaling. We have shown that TRPM7 acts as a sensor of Mg(2+)-availability, adjusting key cellular functions such as the rate of cellular protein translation to the Mg(2+) nutritional status. Since molecular mechanisms controlling rates of protein translation are critical for cell growth and division in response to nutrient availability, this could have relevance for example for therapies targeted at molecules shaping the cancerous translational apparatus. In our quest to understand the biology of Mg(2+) in the context of immune responses, we found that TRPM7 associates with, and phosphorylates phospholipase C gamma 2 (PLCγ2), a pivotal molecule in the signaling pathway following B-cell receptor (BCR) activation. This contributes to the Mg(2+)-dependent modulation of the Ca(2+) response elicited by BCR ligation, and provides the first molecular pathway underlying the Mg(2+)-sensitivity of immune responses. Expanding our knowledge about the modulation of immunoreceptor signaling in response to Mg(2+) availability could allow for the development of unexplored strategies for therapeutic intervention in autoimmune diseases, immunodeficiencies, and lymphoma.

The TRPM6 kinase domain determines the Mg·ATP sensitivity of TRPM7/M6 heteromeric ion channels.

The transient receptor potential melastatin member 7 (TRPM7) and member 6 (TRPM6) are divalent cation channel kinases essential for magnesium (Mg(2+)) homeostasis in vertebrates. It remains unclear how TRPM6 affects divalent cation transport and whether this involves functional homomeric TRPM6 plasma membrane channels or heteromeric channel assemblies with TRPM7. We show that homomeric TRPM6 is highly sensitive to intracellular free Mg(2+) and therefore unlikely to be active at physiological levels of [Mg(2+)]i. Co-expression of TRPM7 and TRPM6 produces heteromeric TRPM7/M6 channels with altered pharmacology and sensitivity to intracellular Mg·ATP compared with homomeric TRPM7. Strikingly, the activity of heteromeric TRPM7/M6 channels is independent of intracellular Mg·ATP concentrations, essentially uncoupling channel activity from cellular energy status. Disruption of TRPM6 kinase phosphorylation activity re-introduces Mg·ATP sensitivity to the heteromeric channel similar to that of TRPM7. Thus, TRPM6 modulates the functionality of TRPM7, and the TRPM6 kinase plays a critical role in tuning the phenotype of the TRPM7·M6 channel complex.

Aldosterone signaling through transient receptor potential melastatin 7 cation channel (TRPM7) and its α-kinase domain.

We demonstrated a role for the Mg(2+) transporter TRPM7, a bifunctional protein with channel and α-kinase domains, in aldosterone signaling. Molecular mechanisms underlying this are elusive. Here we investigated the function of TRPM7 and its α-kinase domain on Mg(2+) and pro-inflammatory signaling by aldosterone. Kidney cells (HEK-293) expressing wild-type human TRPM7 (WThTRPM7) or constructs in which the α-kinase domain was deleted (ΔKinase) or rendered inactive with a point mutation in the ATP binding site of the α-kinase domain (K1648R) were studied. Aldosterone rapidly increased [Mg(2+)]i and stimulated NADPH oxidase-derived generation of reactive oxygen species (ROS) in WT hTRPM7 and TRPM7 kinase dead mutant cells. Translocation of annexin-1 and calpain-II and spectrin cleavage (calpain target) were increased by aldosterone in WT hTRPM7 cells but not in α-kinase-deficient cells. Aldosterone stimulated phosphorylation of MAP kinases and increased expression of pro-inflammatory mediators ICAM-1, Cox-2 and PAI-1 in Δkinase and K1648R cells, effects that were inhibited by eplerenone (mineralocorticoid receptor (MR) blocker). 2-APB, a TRPM7 channel inhibitor, abrogated aldosterone-induced Mg(2+) responses in WT hTRPM7 and mutant cells. In 2-APB-treated ΔKinase and K1648R cells, aldosterone-stimulated inflammatory responses were unchanged. These data indicate that aldosterone stimulates Mg(2+) influx and ROS production in a TRPM7-sensitive, kinase-insensitive manner, whereas activation of annexin-1 requires the TRPM7 kinase domain. Moreover TRPM7 α-kinase modulates inflammatory signaling by aldosterone in a TRPM7 channel/Mg(2+)-independent manner. Our findings identify novel mechanisms for non-genomic actions of aldosterone involving differential signaling through MR-activated TRPM7 channel and α-kinase.

The role of Mg2+ in immune cells.

The physiological and clinical relevance of Mg(2+) has evolved over the last decades. The molecular identification of multiple Mg(2+) transporters (Acdp2, MagT1, Mrs2, Paracellin-1, SLC41A1, SLC41A2, TRPM6 and TRPM7) and their biophysical characterization in recent years has improved our understanding of Mg(2+) homeostasis regulation and has provided a basis for investigating the role of Mg(2+) in the immune system. Deletions and mutations of Mg(2+) transporters produce severe phenotypes with more systemic symptoms than those seen with Ca(2+) channel deletions, which tend to be more specific and less profound. Deficiency of the Mg(2+) permeable ion channels TRPM6 or TRPM7 in mice is lethal at embryonic day 12.5 or at day 6.5, respectively, and, even more surprisingly, chicken DT40 B cells lacking TRPM7 die after 24-48 h. Recent progress made in Mg(2+) research has helped to define underlying mechanisms of two hereditary diseases, human Hypomagnesemia (TRPM6 deletion) and X-chromosomal immunodeficiency (MagT1 deletion), and has revealed a potential new role for Mg(2+) as a second messenger. Future elucidation of human Mg(2+) transporters (Mrs2, SLC41A1, SLC41A2, TRPM7) expressed in immunocytes, beyond MagT1 and TRPM6, will widen our knowledge about the potential role of Mg(2+) in the activation of the immune response.

Advanced error identification in deposition of complex optical layer systems by a multianalyzing approach.

If a new complex optical multilayer system, coating chamber, material, or design has to be evaluated, there is often a need for several test deposition runs until most significant errors and coating properties are identified. We present an advanced procedure with combination of an optical broadband thickness monitor, computational manufacturing, and automated reoptimization, which requires only one single test deposition run. For the identification of material and deposition errors, the single test deposition run is evaluated by the computational manufacturing using different parameter sets. Determined main errors are corrected (e.g., dispersion), and remaining smaller errors will be compensated with the automated reoptimization tool as an expansion of the optical monitor.

Identification of Ser/Thr phosphorylation sites in the C2-domain of phospholipase C γ2 (PLCγ2) using TRPM7-kinase.

PLC-isozymes are central elements of cellular signaling downstream of numerous receptors. PLCγ2 is a pivotal component of B cell receptor (BCR) signaling. The regulation of PLCγ2-dependent signaling functions by Tyr-phosphorylation is well characterized, however, the potential role of Ser/Thr phosphorylation events remains undefined. TRPM7 is the fusion of a Ser/Thr kinase with an ion channel, and an essential component of Mg(2+)-homeostasis regulation. Although the interaction between the C2 domain of several PLC-isozymes and TRPM7 is well established, previous studies have focused on the effect of PLC-activity on TRPM7. Here, we investigated whether Ser/Thr phosphorylation sites in the C2 domain of PLCγ2 could be identified using TRPM7-kinase. We show that TRPM7-kinase phosphorylates PLCγ2 in its C2-domain at position Ser1164 and in the linker region preceding the C2-domain at position Thr1045. Using a complementation approach in PLCγ2(-/-) DT40 cells, we found that the PLCγ2-S1164A mutant fully restores BCR mediated Ca(2+)-responses under standard growth conditions. However, under hypomagnesic conditions, PLCγ2-S1164A fails to reach Ca(2+)-levels seen in cells expressing PLCγ2 wildtype. These results suggest that Mg(2+)-sensitivity of the BCR signaling pathway may be regulated by Ser/Thr phosphorylation of PLCγ2.

The Mg2+ transporter MagT1 partially rescues cell growth and Mg2+ uptake in cells lacking the channel-kinase TRPM7.

Magnesium (Mg(2+)) transport across membranes plays an essential role in cellular growth and survival. TRPM7 is the unique fusion of a Mg(2+) permeable pore with an active cytosolic kinase domain, and is considered a master regulator of cellular Mg(2+) homeostasis. We previously found that the genetic deletion of TRPM7 in DT40 B cells results in Mg(2+) deficiency and severe growth impairment, which can be rescued by supplementation with excess extracellular Mg(2+). Here, we show that gene expression of the Mg(2+) selective transporter MagT1 is upregulated in TRPM7(-/-) cells. Furthermore, overexpression of MagT1 in TRPM7(-/-) cells augments their capacity to uptake Mg(2+), and improves their growth behavior in the absence of excess Mg(2+).

The channel-kinase TRPM7 regulates phosphorylation of the translational factor eEF2 via eEF2-k.

Protein translation is an essential but energetically expensive process, which is carefully regulated in accordance to the cellular nutritional and energy status. Eukaryotic elongation factor 2 (eEF2) is a central regulation point since it mediates ribosomal translocation and can be inhibited by phosphorylation at Thr56. TRPM7 is the unique fusion of an ion channel with a functional Ser/Thr-kinase. While TRPM7's channel function has been implicated in regulating vertebrate Mg(2+) uptake required for cell growth, the function of its kinase domain remains unclear. Here, we show that under conditions where cell growth is limited by Mg(2+) availability, TRPM7 via its kinase mediates enhanced Thr56 phosphorylation of eEF2. TRPM7-kinase does not appear to directly phosphorylate eEF2, but rather to influence the amount of eEF2's cognate kinase eEF2-k, involving its phosphorylation at Ser77. These findings suggest that TRPM7's structural duality ensures ideal positioning of its kinase in close proximity to channel-mediated Mg(2+) uptake, allowing for the adjustment of protein translational rates to the availability of Mg(2+).

Evidence for potassium carbonate crystallites on air-cleaved mica surfaces.

Air-cleaved mica surfaces exhibit a high density of nanometer or micrometer size particles that have been ascribed to potassium carbonate formed as a reaction product of carbonaceous gases with potassium ions. Unambiguous evidence for this assignment has, however, never been presented. We study air-cleaved mica surfaces by high-resolution noncontact atomic force microscopy (NC-AFM) in ultrahigh vacuum to reveal the detailed structure of such precipitates on the surface. Among a large number of irregularly shaped surface structures, we find flat, hexagonally shaped islands exhibiting two different patterns on their surfaces, namely a rectangular atomic corrugation pattern and a hexagonal moire structure. The unit cell of the rectangular pattern corresponds to the dimensions of the potassium carbonate bulk structure and is found on high crystallites. The moire structure solely appears on very flat islands and is caused by the interference of the potassium carbonate lattice periodicity and the lattice periodicity of the underlying mica substrate. Both results strongly point to the presence of potassium carbonate crystallites on air-cleaved mica surfaces.

Altered functional properties of a TRPM2 variant in Guamanian ALS and PD.

Two related neurodegenerative disorders, Western Pacific amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD), originally occurred at a high incidence on Guam, in the Kii peninsula of Japan, and in southern West New Guinea more than 50 years ago. These three foci shared a unique mineral environment characterized by the presence of severely low levels of Ca(2+) and Mg(2+), coupled with high levels of bioavailable transition metals in the soil and drinking water. Epidemiological studies suggest that genetic factors also contribute to the etiology of these disorders. Here, we report that a variant of the transient receptor potential melastatin 2 (TRPM2) gene may confer susceptibility to these diseases. TRPM2 encodes a calcium-permeable cation channel highly expressed in the brain that has been implicated in mediating cell death induced by oxidants. We found a heterozygous variant of TRPM2 in a subset of Guamanian ALS (ALS-G) and PD (PD-G) cases. This variant, TRPM2(P1018L), produces a missense change in the channel protein whereby proline 1018 (Pro(1018)) is replaced by leucine (Leu(1018)). Functional studies revealed that, unlike WT TRPM2, P1018L channels inactivate. Our results suggest that the ability of TRPM2 to maintain sustained ion influx is a physiologically important function and that its disruption may, under certain conditions, contribute to disease states.