Chronic pain hypersensitivity depends on N-type voltage-gated calcium channels (CaV2.2). However, the use of CaV2.2 blockers in pain therapeutics is limited by side effects that result from inhibited physiological functions of these channels. Here we report suppression of both inflammatory and neuropathic hypersensitivity by inhibiting the binding of the axonal collapsin response mediator protein 2 (CRMP-2) to CaV2.2, thus reducing channel function. A 15-amino acid peptide of CRMP-2 fused to the transduction domain of HIV TAT protein (TAT-CBD3) decreases neurotransmitter release from nociceptive dorsal root ganglion neurons, reduces meningeal blood flow, reduces nocifensive behavior induced by subcutaneous formalin injection or following corneal capsaicin application, and reverses neuropathic hypersensitivity produced by the antiretroviral drug 2’,3’-dideoxycytidine. TAT-CBD3 was mildly anxiolytic but innocuous on sensorimotor and cognitive functions and despair. By preventing CRMP-2-mediated enhancement of CaV2.2 function, TAT-CBD3 alleviates inflammatory and neuropathic hypersensitivity, an approach that may prove useful in managing clinical pain.

Neurological disorders develop in most people infected with human immunodeficiency virus type 1 (HIV-1). However, the underlying mechanisms remain largely unknown. Here we report that binding of HIV-1 transactivator (Tat) protein to low-density lipoprotein receptor-related protein (LRP) promoted efficient uptake of Tat into neurons. LRP-mediated uptake of Tat was followed by translocation to the neuronal nucleus. Furthermore, the binding of Tat to LRP resulted in substantial inhibition of neuronal binding, uptake and degradation of physiological ligands for LRP, including alpha2-macroglobulin, apolipoprotein E4, amyloid precursor protein and amyloid beta-protein. In a model of macaques infected with a chimeric strain of simian-human immunodeficiency virus, increased staining of amyloid precursor protein was associated with Tat expression in the brains of simian-human immunodeficiency virus-infected macaques with encephalitis. These results indicate that HIV-1 Tat may mediate HIV-1-induced neuropathology through a pathway involving disruption of the metabolic balance of LRP ligands and direct activation of neuronal genes.

Collapsin response mediator proteins (CRMPs) mediate signal transduction of neurite outgrowth and axonal guidance during neuronal development. Voltage-gated Ca2+ channels and interacting proteins are essential in neuronal signaling and synaptic transmission during this period. We recently identified the presynaptic N-type voltage-gated Ca2+ channel (Cav2.2) as a CRMP-2-interacting partner. Here, we investigated the effects of a functional association of CRMP-2 with Cav2.2 in sensory neurons. Cav2.2 colocalized with CRMP-2 at immature synapses and growth cones, in mature synapses and in cell bodies of dorsal root ganglion (DRG) neurons. Co-immunoprecipitation experiments showed that CRMP-2 associates with Cav2.2 from DRG lysates. Overexpression of CRMP-2 fused to enhanced green fluorescent protein (EGFP) in DRG neurons, via nucleofection, resulted in a significant increase in Cav2.2 current density compared with cells expressing EGFP. CRMP-2 manipulation changed the surface levels of Cav2.2. Because CRMP-2 is localized to synaptophysin-positive puncta in dense DRG cultures, we tested whether this CRMP-2-mediated alteration of Ca2+ currents culminated in changes in synaptic transmission. Following a brief high-K+-induced stimulation, these puncta became loaded with FM4-64 dye. In EGFP and neurons expressing CRMP-2–EGFP, similar densities of FM-loaded puncta were observed. Finally, CRMP-2 overexpression in DRG increased release of the immunoreactive neurotransmitter calcitonin gene-related peptide (iCGRP) by ∼70%, whereas siRNA targeting CRMP-2 significantly reduced release of iCGRP by ∼54% compared with control cultures. These findings support a novel role for CRMP-2 in the regulation of N-type Ca2+ channels and in transmitter release.

Summary BACKGROUND Plexiform neurofibromas (PN) are slow growing chemoradiotherapy resistant tumours arising in patients with neurofibromatosis type I (NF1). Currently there are no viable therapeutic options for patients whose life-threatening plexiform neurofibromas cannot be surgically removed due to proximity to vital body structures. Based on identification of molecular targets in genetic mouse models of human NF1 tumours, we hypothesized that the oral kinase inhibitor, imatinib mesylate, may be effective in targeted treatment of these chemoradiotherapy-refractory tumours. METHODS An open-label pilot Phase II clinical trial was designed to test whether treatment with imatinib mesylate can decrease volume burden of clinically significant plexiform neurofibromas in NF1 patients. The entry criteria require patients only to have NF1 and a clinically significant plexiform neurofibroma with the specified age limitations (age 3–65). Patients were treated with daily oral imatinib at 440 mg/m2/day for children and 800 mg/day for adults divided twice daily for 6 months. The primary endpoint measure of significant response was a 20% or more reduction in plexiform size by sequential volumetric MRI imaging. Clinical data was analyzed on an intent to treat basis, however to determine the activity of imatinib on NF1-related plexiform tumours, patients able to take imatinib for 6 months were evaluated for their response. Secondary outcomes included evaluation of safety of imatinib mesylate in this group of patients. The trial is registered at http://clinicaltrials.gov/; study number 0512-25. The trial currently is closed to enrollment, however there is a single patient that continues to respond and remains on study. FINDINGS On an intent to treat basis, 6 out of 36 patients or 17% (95% CI: 6 – 33%) experienced objective response to imatinib mesylate. In the evaluable study population of patients (n=23) who received drug for at least six months, six patients (26%; 95% CI: 10 – 48%) experienced ≥ 20% decrease in volume of one or more plexiform tumours and 30% of study patients had symptomatic improvement. We noted significant inter-patient and intra-patient heterogeneity of plexiform neurofibroma response. Toxicity of drug was comparable to previous reports in patients with chronic myelogenous leukemia. The most common adverse events were reversible skin rash (5 patients) and edema with weight gain (6 patients). More serious adverse events included reversible grade 3 neutropenia (2 patients) and grade 4 transaminitis (one patient). INTERPRETATION Imatinib mesylate caused disease regression in 26% of evaluable patients with clinically significant plexiform neurofibromas due to neurofibromatosis type 1. These results warrant confirmation in a larger multi-institutional clinical trial aimed at this patient population. These findings provide the first demonstration of radiographic volumetric tumour reduction in response to medical therapy in patients with NF1 plexiform neurofibromas using imatinib mesylate based on studies...

Neurofibromatosis type 1 (NF1) results from mutations in the NF1 tumor suppressor gene, which encodes the protein neurofibromin. NF1 patients display diverse clinical manifestations, including vascular disease, which results from neointima formation and vessel occlusion. However, the pathogenesis of NF1 vascular disease remains unclear. Vessel wall homeostasis is maintained by complex interactions between vascular and bone marrow-derived cells (BMDCs), and neurofibromin regulates the function of each cell type. Therefore, utilizing cre/lox techniques and hematopoietic stem cell transplantation to delete 1 allele of Nf1 in endothelial cells, vascular smooth muscle cells, and BMDCs alone, we determined which cell lineage is critical for neointima formation in vivo in mice. Here we demonstrate that heterozygous inactivation of Nf1 in BMDCs alone was necessary and sufficient for neointima formation after vascular injury and provide evidence of vascular inflammation in Nf1 +/-mice. Further, analysis of peripheral blood from NF1 patients without overt vascular disease revealed increased concentrations of inflammatory cells and cytokines previously linked to vascular inflammation and vasoocclusive disease. These data provide genetic and cellular evidence of vascular inflammation in NF1 patients and Nf1 +/-mice and provide a framework for understanding the pathogenesis of NF1 vasculopathy and potential therapeutic and diagnostic interventions. IntroductionNeurofibromatosis type 1 (NF1) is an autosomal dominant disorder that results from mutations in the tumor suppressor gene NF1 (1). Neurofibromin, the protein product of NF1, functions as a p21 Ras (Ras) GTPase-activating protein (GAP) to negatively regulate Ras activity (2). More than 240 different mutations have been described within the NF1 gene, all of which result in little or no protein product (3). While loss of heterozygosity has been described in primary tumor samples (4), the germline mutations that cause NF1 affect only 1 copy of the NF1 gene. Haploinsufficiency of NF1 results in disease with complete penetrance and a range of clinical complications.The most common clinical manifestations of NF1 include dermal and plexiform neurofibromas, learning deficits, and skeletal abnormalities. Vascular disease associated with NF1 is an underrecognized complication that results in increased morbidity and mortality, particularly among younger patients (5, 6). In 2001, an analysis of 3,253 death certificates of persons with NF1 indicated that the median age of death for NF1 patients was 15 years lower that of the general population (6). In this report, a diagnosis suggestive of NF1 vasculopathy was listed 7.2 times more often than expected among NF1 patients less than 30 years old at time of death and 2.2 times more often than expected among patients 30-40 years old at the time of death (6). Another study demonstrated that 2.5% of children with NF1 who had undergone brain MRI were found to have cerebrovascular system abnormalities including narrowed vessels, moyamoya, va...