Tatsuhiko Matsuoka

Nardilysin regulates axonal maturation and myelination in the central and peripheral nervous system

Axonal maturation and myelination are essential processes for establishing an efficient neuronal signaling network. We found that nardilysin (N-arginine dibasic convertase, also known as Nrd1 and NRDc), a metalloendopeptidase enhancer of protein ectodomain shedding, is a critical regulator of these processes. Nrd1−/− mice had smaller brains and a thin cerebral cortex, in which there were less myelinated fibers with thinner myelin sheaths and smaller axon diameters. We also found hypomyelination in the peripheral nervous system (PNS) of Nrd1−/− mice. Neuron-specific overexpression of NRDc induced hypermyelination, indicating that the level of neuronal NRDc regulates myelin thickness. Consistent with these findings, Nrd1−/− mice had impaired motor activities and cognitive deficits. Furthermore, NRDc enhanced ectodomain shedding of neuregulin1 (NRG1), which is a master regulator of myelination in the PNS. On the basis of these data, we propose that NRDc regulates axonal maturation and myelination in the CNS and PNS, in part, through the modulation of NRG1 shedding.

Ectodomain shedding of TNF-α is enhanced by nardilysin via activation of ADAM proteases

Tumor necrosis factor-alpha (TNF-alpha) is released from cells by proteolytic cleavage of a membrane-anchored precursor. The TNF-alpha-converting enzyme (TACE/ADAM17) is the major sheddase for ectodomain shedding of TNF-alpha. At present, however, it is poorly understood how its catalytic activity is regulated. Here, we show that nardilysin (N-arginine dibasic convertase; NRDc) enhanced TNF-alpha shedding. In a cell-based shedding assay, expression of NRDc synergistically enhanced TACE-induced TNF-alpha shedding. A peptide cleavage assay in vitro showed that recombinant NRDc enhances the cleavage of TNF-alpha induced by TACE. Notably, co-incubation of NRDc completely reversed the inhibitory effect of a physiological concentration of salt on TACEs activity in vitro. Overexpression of NRDc in TACE-deficient fibroblasts resulted in an increase in the amount of TNF-alpha released. Co-expression of NRDc with ADAM10 promoted the release compared with the sole expression of ADAM10. These results suggested that NRDc enhances TNF-alpha shedding through activation of not only TACE but ADAM10. Our results indicate the involvement of NRDc in ectodomain shedding of TNF-alpha, which may be a novel target for anti-inflammatory therapies.

Critical roles of nardilysin in the maintenance of body temperature homoeostasis

Body temperature homoeostasis in mammals is governed centrally through the regulation of shivering and non-shivering thermogenesis and cutaneous vasomotion. Non-shivering thermogenesis in brown adipose tissue (BAT) is mediated by sympathetic activation, followed by PGC-1α induction, which drives UCP1. Here we identify nardilysin (Nrd1 and NRDc) as a critical regulator of body temperature homoeostasis. Nrd1−/− mice show increased energy expenditure owing to enhanced BAT thermogenesis and hyperactivity. Despite these findings, Nrd1−/− mice show hypothermia and cold intolerance that are attributed to the lowered set point of body temperature, poor insulation and impaired cold-induced thermogenesis. Induction of β3-adrenergic receptor, PGC-1α and UCP1 in response to cold is severely impaired in the absence of NRDc. At the molecular level, NRDc and PGC-1α interact and co-localize at the UCP1 enhancer, where NRDc represses PGC-1α activity. These findings reveal a novel nuclear function of NRDc and provide important insights into the mechanism of thermoregulation.

Nardilysin prevents amyloid plaque formation by enhancing α-secretase activity in an Alzheimer's disease mouse model

Amyloid beta (Aβ) peptide, the main component of senile plaques in patients with Alzheimers disease (AD), is derived from proteolytic cleavage of amyloid precursor protein (APP) by β- and γ-secretases. Alpha-cleavage of APP by α-secretase has a potential to preclude the generation of Aβ because it occurs within the Aβ domain. We previously reported that a metalloendopeptidase, nardilysin (N-arginine dibasic convertase; NRDc) enhances α-cleavage of APP, which results in the decreased generation of Aβ in vitro. To clarify the in vivo role of NRDc in AD, we intercrossed transgenic mice expressing NRDc in the forebrain with an AD mouse model. Here we demonstrate that the neuron-specific overexpression of NRDc prevents Aβ deposition in the AD mouse model. The activity of α-secretase in the mouse brain was enhanced by the overexpression of NRDc, and was reduced by the deletion of NRDc. However, reactive gliosis adjacent to the Aβ plaques, one of the pathological features of AD, was not affected by the overexpression of NRDc. Taken together, our results indicate that NRDc controls Aβ formation through the regulation of α-secretase.

The clinical and hemodynamic factors that influence the concentrations of biomarkers of myocyte injury measured by high sensitive assay PATHFAST

BACKGROUND Subclinical myocyte injury plays an important role in the progression of congestive heart failure. However, the clinical and hemodynamic factors that influence the concentrations of biomarkers of myocyte injury have not been clarified. METHODS Blood was sampled during diagnostic cardiac catheterization from 108 consecutive patients without acute coronary syndrome and acute cardiac decompensation. The serum concentrations of B-type natriuretic peptide (BNP), cardiac troponin I (cTnI), creatine kinase (CK)-MB, and myoglobin were measured simultaneously by high sensitive PATHFAST assay. Single and multiple variable regression analyses were carried out in search of correlations between clinical and hemodynamic variables and concentrations of biomarkers. RESULTS By multiple variable analysis, hemoglobin concentration, pulmonary capillary wedge pressure (PCWP), left ventricular (LV) ejection fraction, and estimated glomerular filtration rate (GFR) were independently correlated with a BNP concentration ≥ median 72.1 pg/ml. The only factors independently correlated with a concentration of cTnI ≥ median 0.01 ng/ml were PCWP and estimated GFR. Cardiac index emerged as a single, powerful, independent correlate of CK-MB concentration ≥ median 0.66 ng/ml, and estimated GFR emerged as a single independent correlate of myoglobin concentration ≥ median 40.1 ng/ml. CONCLUSIONS Clinical and hemodynamic factors influence the concentrations of BNP, cTnI, CK-MB, and myoglobin. These factors should be considered when interpreting the concentrations of these biochemical markers.