Characterization of Antibodies against Receptor Activity-Modifying Protein 1 (RAMP1): A Cautionary Tale

Calcitonin gene-related peptide (CGRP) is a key component of migraine pathophysiology, yielding effective migraine therapeutics. CGRP receptors contain a core accessory protein subunit: receptor activity-modifying protein 1 (RAMP1). Understanding of RAMP1 expression is incomplete, partly due to the challenges in identifying specific and validated antibody tools. We profiled antibodies for immunodetection of RAMP1 using Western blotting, immunocytochemistry and immunohistochemistry, including using RAMP1 knockout mouse tissue. Most antibodies could detect RAMP1 in Western blotting and immunocytochemistry using transfected cells. Two antibodies (844, ab256575) could detect a RAMP1-like band in Western blots of rodent brain but not RAMP1 knockout mice. However, cross-reactivity with other proteins was evident for all antibodies. This cross-reactivity prevented clear conclusions about RAMP1 anatomical localization, as each antibody detected a distinct pattern of immunoreactivity in rodent brain. We cannot confidently attribute immunoreactivity produced by RAMP1 antibodies (including 844) to the presence of RAMP1 protein in immunohistochemical applications in brain tissue. RAMP1 expression in brain and other tissues therefore needs to be revisited using RAMP1 antibodies that have been comprehensively validated using multiple strategies to establish multiple lines of convincing evidence. As RAMP1 is important for other GPCR/ligand pairings, our results have broader significance beyond the CGRP field

An Inflammatory Cascade Leading to Hyperresistinemia in Humans

BACKGROUND: Obesity, the most common cause of insulin resistance, is increasingly recognized as a low-grade inflammatory state. Adipocyte-derived resistin is a circulating protein implicated in insulin resistance in rodents, but the role of human resistin is uncertain because it is produced largely by macrophages. METHODS AND FINDINGS: The effect of endotoxin and cytokines on resistin gene and protein expression was studied in human primary blood monocytes differentiated into macrophages and in healthy human participants. Inflammatory endotoxin induced resistin in primary human macrophages via a cascade involving the secretion of inflammatory cytokines that circulate at increased levels in individuals with obesity. Induction of resistin was attenuated by drugs with dual insulin-sensitizing and anti-inflammatory properties that converge on NF-κB. In human study participants, experimental endotoxemia, which produces an insulin-resistant state, causes a dramatic rise in circulating resistin levels. Moreover, in patients with type 2 diabetes, serum resistin levels are correlated with levels of soluble tumor necrosis factor α receptor, an inflammatory marker linked to obesity, insulin resistance, and atherosclerosis. CONCLUSIONS: Inflammation is a hyperresistinemic state in humans, and cytokine induction of resistin may contribute to insulin resistance in endotoxemia, obesity, and other inflammatory states

ASIC1A in the bed nucleus of the stria terminalis mediates TMT-evoked freezing

Mice display an unconditioned freezing response to TMT, a predator odor isolated from fox feces. Here we found that in addition to freezing, TMT caused mice to decrease breathing rate, perhaps because of the aversive smell. Consistent with this possibility, olfactory bulb lesions attenuated this effect of TMT, as well as freezing. Interestingly, butyric acid, another foul odor, also caused mice to reduce breathing rate. However, unlike TMT, butyric acid did not induce freezing. Thus, although these aversive odors may affect breathing, the unpleasant smell and suppression of breathing by themselves are insufficient to cause freezing. Because the acid-sensing ion channel-1A (ASIC1A) has been previously implicated in TMT-evoked freezing, we tested whether Asic1a disruption also altered breathing. We found that TMT reduced breathing rate in both Asic1a+/+ and Asic1a–/– mice, suggesting that ASIC1A is not required for TMT to inhibit breathing and that the absence of TMT-evoked freezing in the Asic1a–/– mice is not due to an inability to detect TMT. These observations further indicate that ASIC1A must affect TMT freezing in another way. Because the bed nucleus of the stria terminalis (BNST) has been critically implicated in TMT-evoked freezing and robustly expresses ASIC1A, we tested whether ASIC1A in the BNST plays a role in TMT-evoked freezing. We disrupted ASIC1A in the BNST of Asic1aloxP/loxP mice by delivering Cre recombinase to the BNST with an adeno-associated virus (AAV) vector. We found that disrupting ASIC1A in the BNST reduced TMT-evoked freezing relative to control mice in which a virus expressing eGFP was injected. To test whether ASIC1A in the BNST was sufficient to increase TMT-evoked freezing, we used another AAV vector to express ASIC1A in the BNST of Asic1a–/– mice. We found region-restricted expression of ASIC1A in the BNST increased TMT-elicited freezing. Together, these data suggest that the BNST is a key site of ASIC1A action in TMT-evoked freezing

Characterization of Antibodies against Receptor Activity-Modifying Protein 1 (RAMP1): A Cautionary Tale

Calcitonin gene-related peptide (CGRP) is a key component of migraine pathophysiology, yielding effective migraine therapeutics. CGRP receptors contain a core accessory protein subunit: receptor activity-modifying protein 1 (RAMP1). Understanding of RAMP1 expression is incomplete, partly due to the challenges in identifying specific and validated antibody tools. We profiled antibodies for immunodetection of RAMP1 using Western blotting, immunocytochemistry and immunohistochemistry, including using RAMP1 knockout mouse tissue. Most antibodies could detect RAMP1 in Western blotting and immunocytochemistry using transfected cells. Two antibodies (844, ab256575) could detect a RAMP1-like band in Western blots of rodent brain but not RAMP1 knockout mice. However, cross-reactivity with other proteins was evident for all antibodies. This cross-reactivity prevented clear conclusions about RAMP1 anatomical localization, as each antibody detected a distinct pattern of immunoreactivity in rodent brain. We cannot confidently attribute immunoreactivity produced by RAMP1 antibodies (including 844) to the presence of RAMP1 protein in immunohistochemical applications in brain tissue. RAMP1 expression in brain and other tissues therefore needs to be revisited using RAMP1 antibodies that have been comprehensively validated using multiple strategies to establish multiple lines of convincing evidence. As RAMP1 is important for other GPCR/ligand pairings, our results have broader significance beyond the CGRP field

Amylin analog pramlintide induces migraine-like attacks in patients

OBJECTIVE: Migraine is a prevalent and disabling neurological disease. Its genesis is poorly understood and there remains unmet clinical need. We aimed to identify mechanisms and thus novel therapeutic targets for migraine using human models of migraine and translational models in animals, with emphasis on amylin, a close relative of calcitonin gene-related peptide (CGRP). METHODS: Thirty-six migraine without aura patients were enrolled in a randomized, double-blinded, two-way, cross-over, positive-controlled clinical trial study to receive infusion of an amylin analogue pramlintide or human αCGRP on two different experimental days. Furthermore, translational studies in cells and mouse models, and rat and human tissue samples were conducted. RESULTS: Thirty patients (88%) developed headache after pramlintide infusion, compared to thirty-three (97%) after CGRP (p = 0.375). Fourteen patients (41%) developed migraine-like attacks after pramlintide infusion, compared to nineteen patients (56%) after CGRP (p = 0.180). The pramlintide induced migraine-like attacks had similar clinical characteristics to those induced by CGRP. There were differences between treatments in vascular parameters. Human receptor pharmacology studies showed that an amylin receptor likely mediates these pramlintide-provoked effects, rather than the canonical CGRP receptor. Supporting this, preclinical experiments investigating symptoms associated with migraine showed that amylin treatment, like CGRP, caused cutaneous hypersensitivity and light aversion in mice. INTERPRETATION: Our findings propose amylin receptor agonism as a novel contributor to migraine pathogenesis. Greater therapeutic gains could therefore be made for migraine patients through dual amylin and CGRP receptor antagonism, rather than selectively targeting the canonical CGRP receptor

Seizures Are Regulated by Ubiquitin-specific Peptidase 9 X-linked (USP9X), a De-Ubiquitinase

<div><p>Epilepsy is a common disabling disease with complex, multifactorial genetic and environmental etiology. The small fraction of epilepsies subject to Mendelian inheritance offers key insight into epilepsy disease mechanisms; and pathologies brought on by mutations in a single gene can point the way to generalizable therapeutic strategies. Mutations in the PRICKLE genes can cause seizures in humans, zebrafish, mice, and flies, suggesting the seizure-suppression pathway is evolutionarily conserved. This pathway has never been targeted for novel anti-seizure treatments. Here, the mammalian PRICKLE-interactome was defined, identifying prickle-interacting proteins that localize to synapses and a novel interacting partner, USP9X, a substrate-specific de-ubiquitinase. PRICKLE and USP9X interact through their carboxy-termini; and USP9X de-ubiquitinates PRICKLE, protecting it from proteasomal degradation. In forebrain neurons of mice, USP9X deficiency reduced levels of Prickle2 protein. Genetic analysis suggests the same pathway regulates Prickle-mediated seizures. The seizure phenotype was suppressed in <i>prickle</i> mutant flies by the small-molecule USP9X inhibitor, Degrasyn/WP1130, or by reducing the dose of <i>fat facets</i> a <i>USP9X</i> orthologue. <i>USP9X</i> mutations were identified by resequencing a cohort of patients with epileptic encephalopathy, one patient harbored a <i>de novo</i> missense mutation and another a novel coding mutation. Both <i>USP9X</i> variants were outside the PRICKLE-interacting domain. These findings demonstrate that USP9X inhibition can suppress <i>prickle</i>-mediated seizure activity, and that <i>USP9X</i> variants may predispose to seizures. These studies point to a new target for anti-seizure therapy and illustrate the translational power of studying diseases in species across the evolutionary spectrum.</p></div

PRICKLE interacts with USP9X via its carboxyl terminal.

<p> <b>A.</b> PRICKLE1 and PRICKLE2 interact with endogenous Bcr, Tanc2, and Usp9x in NGF-differentiated PC12 cells. GFP immunoprecipitates from stable lines expressing GFP, GFP-PRICKLE1 or GFP-PRICKLE2 confirm that PRICKLE interacts with Bcr, Usp9x and Tanc2. <b>B</b>. Flag immunoprecipitates, from HEK293T cells overexpressing flag-tagged PRICKLE1 or PRICKLE2, show endogenous USP9X physically interacts with PRICKLE. <b>C, D.</b> Schematic of PRICKLE1(C) and PRICKLE2(D) constructs. Flag-immunoprecipitates from HEK293T cells overexpressing the indicated constructs were analyzed by anti-USP9X Western blotting. Both PRICKLE 1 and 2 interact with USP9X via their C-termini while BCR binding mapped to their N-termini.</p

USP9X stabilizes PRICKLE in HEK293T cells and the mouse brain.

<p> <b>A</b>. Flag-immunoprecipitates from HEK293T cells overexpressing the indicated constructs show PRICKLE and USP9X interact via their carboxyl termini. <b>B, C.</b> USP9X deubiquitinates PRICKLE. Immunoprecipitates from HEK293T cells overexpressing the indicated constructs show PRICKLE ubiquitination in the presence of HA-Ubiquitin and deubiquitination/stabilization by Usp9x. IP (immunoprecipitates), IN (input). <b>D.</b> Loss of Usp9X affects Prickle2 (green) expression. Deletion of Usp9x results in decreased Prickle2 expression in the cortex (I), CA1 (II) and dentate gyrus (III) of 4-week old mice when compared to controls (IV, V, VI). n = 2. Scale bar:20μM. Nuclear stain = DAPI.</p