Biomedical subjects

Hai-Yan Wu

Publications and source records attributed to Hai-Yan Wu.

7 recordsLinked to original sources

PubMed2006

Developmental and cell-selective variations in N-methyl-D-aspartate receptor degradation by calpain.

NMDA receptors play critical roles in synaptic modulation and neurological disorders. In this study, we investigated the developmental changes in NR2 cleavage by NMDA receptor-activated calpain in cultured cortical and hippocampal neurons. Calpain activity increased with development, associated with increased expression of NMDA receptors but not of calpain I. The activation of calpain in immature and mature cortical cultures was inhibited by antagonists of NR1/2B and NR1/2A/2B receptors, whereas the inhibition of NR1/2B receptors did not alter calpain activation in mature hippocampal cultures. The degradation of NR2 subunits by calpain differed with developmental age. NR2A was not a substrate of calpain in mature hippocampal cultures, but was cleaved in immature cortical and hippocampal cultures. NR2B degradation by calpain in cortical cultures decreased with development, but the level of degradation of NR2B in hippocampal cultures did not change. The kinetics of NMDA receptor-gated whole cell currents were also modulated by calpain activation in a manner that varied with developmental stage in vitro. In early (but not later) developmental stages, calpain activation altered the NMDA-evoked current rise time and time constants for both desensitization and deactivation. Our data suggest that the susceptibility of the NMDA receptor to cleavage by calpain varies with neuronal maturity in a manner that may alter its electrophysiological properties.

Aging↗

PubMed2006

Calpain and synaptic function.

Proteolysis by calpain is a unique posttranslational modification that can change integrity, localization, and activity of endogenous proteins. Two ubiquitous calpains, mu-calpain and m-calpain, are highly expressed in the central nervous system, and calpain substrates such as membrane receptors, postsynaptic density proteins, kinases, and phosphatases are localized to the synaptic compartments of neurons. By selective cleavage of synaptically localized molecules, calpains may play pivotal roles in the regulation of synaptic processes not only in physiological states but also during various pathological conditions. Activation of calpains during sustained synaptic activity is crucial for Ca2+-dependent neuronal functions, such as neurotransmitter release, synaptic plasticity, vesicular trafficking, and structural stabilization. Overactivation of calpain following dysregulation of Ca2+ homeostasis can lead to neuronal damage in response to events such as epilepsy, stroke, and brain trauma. Calpain may also provide a neuroprotective effect from axotomy and some forms of glutamate receptor overactivation. This article focuses on recent findings on the role of calpain-mediated proteolytic processes in potentially regulating synaptic substrates in physiological and pathophysiological events in the nervous system.

Animals↗

PubMed2005

Regulation of N-methyl-D-aspartate receptors by calpain in cortical neurons.

The N-methyl-D-aspartate (NMDA) receptor is a cation channel highly permeable to calcium and plays critical roles in governing normal and pathologic functions in neurons. Calcium entry through NMDA receptors (NMDARs) can lead to the activation of the Ca2+-dependent protease, calpain. Here we investigated the involvement of calpain in regulation of NMDAR channel function. After prolonged (5-min) treatment with NMDA or glutamate, the whole-cell NMDAR-mediated current was significantly reduced in both acutely dissociated and cultured cortical pyramidal neurons. The down-regulation of NMDAR current was blocked by bath application of selective calpain inhibitors. Intracellular injection of a specific calpain inhibitory peptide also eliminated the down-regulation of NMDAR current induced by prolonged NMDA treatment. In contrast, dynamin inhibitory peptide had no effect on the depression of NMDAR current, suggesting the lack of involvement of dynamin/clathrin-mediated NMDAR internalization in this process. Immunoblotting analysis showed that the NR2A and NR2B subunits of NMDARs were markedly degraded in cultured cortical neurons treated with glutamate, and the degradation of NR2 subunits was prevented by calpain inhibitors. Taken together, our results suggest that prolonged activation of NMDARs in neurons activates calpain, and activated calpain in turn down-regulates the function of NMDARs, which provides a neuroprotective mechanism against NMDAR overstimulation accompanying ischemia and stroke.

Animals↗

PubMed2004

HIV-1 Tat inhibits long-term potentiation and attenuates spatial learning [corrected].

Although memory deficits have been clearly documented in patients with human immunodeficiency virus type-1 (HIV-1) infection, the physiological basis of this dysfunction is poorly understood. We focused on Tat, a viral protein released from HIV-1-infected cells and investigated its effect on spatial learning in adult mice. An intracerebroventricular injection of Tat leads to attenuation of spatial learning accompanied by suppression of long-term potentiation (LTP), the cellular basis of spatial learning, in hippocampal cornu ammonis 1 pyramidal neurons. Tat facilitates extrasynaptic but not synaptic N-methyl-D-aspartate (NMDA) receptor activity. Taken together, these data provide strong evidence that the Tat pathway underlies the development of memory dysfunction in patients with HIV-1 infection and suggest a causal relationship between Tat, the facilitation of extrasynaptic NMDA receptor activity, inhibition of LTP, and attenuation of spatial learning.

Animals↗

PubMed2003

Critical role of calpain-mediated cleavage of calcineurin in excitotoxic neurodegeneration.

Calcineurin and calpain, a Ca2+/calmodulin-dependent protein phosphatase and a Ca2+-dependent cysteine protease, respectively, mediate neuronal cell death through independent cascades. Here, we report that during neuroexcitotoxicity, calcineurin A (CnA) is directly cleaved by calpain in vitro and in vivo, resulting in the enzyme being converted to an active form. Mass spectrometry identified three cleavage sites in CnA, two of which were constitutively active forms. Overexpression of the cleaved CnA induced caspase activity and neuronal cell death. Calpain inhibitors and membrane-permeable calpastatin peptides not only blocked the cleavage of CnA, but also protected against excitotoxic neuronal cell death in vitro and in vivo. These results indicate that CnA is a crucial target for calpain, and the calpain-mediated activation of CnA triggers excitotoxic neurodegeneration. This study established a molecular link between calpain and calcineurin, thereby demonstrating a new mechanism for proteolytical regulation of calcineurin by calpain in response to certain pathological states.

Amino Acid Sequence↗

PubMed2003

Poly-arginine-fused calpastatin peptide, a living cell membrane-permeable and specific inhibitor for calpain.

Calpain, a Ca2+-dependent neutral protease, is highly related to the pathogenesis of a variety of disorders and its inhibitors offer potential for therapeutic intervention. General calpain inhibitors, however, have the disadvantage of a lack of specificity or poor cellular permeability or oxidization under physiological conditions. Here, we developed a membrane-permeable specific calpain inhibitor by fusing calpastatin peptide (CS) and 11 poly-arginine peptides (11R). The 11R-fused CS (11R-CS) effectively penetrated across the plasma membrane of living neurons and significantly inhibited calpain activity in the cells.

Animals↗

PubMed2002

Diversity of rotavirus strains among children with acute diarrhea in China: 1998-2000 surveillance study.

As part of a national rotavirus surveillance activity, we collected fecal specimens from 3,177 children with acute diarrhea in 10 regions of China between April 1998 and April 2000 and screened them for rotavirus. Rotavirus was detected in 41% (n = 1,305) of specimens, and in these, G1 was the predominant serotype (72.6%), followed by G3 (14.2%), G2 (12.1%), G4 (2.5%), G9 (0.9%), and G untypeable (0.7%). Among 327 G-typed strains tested for P genotype, 14 different P-G combinations were identified, with the globally common strains P[8]G1, P[4]G2, P[8]G3, and P[8]G4 representing 75.6% of all typed rotavirus strains. Among the uncommon strains, 11 were P[6]G9, and others included P[6]G1, P[6]G3, and five novel P-G combinations (P[9]G1, P[4]G1, P[4]G3, P[4]G4, and P[8]G2). Our results indicate that while the common rotavirus strains remain predominant, the diversity of strains is much greater than was previously recognized.

Acute Disease↗