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Phospholipase A2 activity-dependent stimulation of Ca2+ entry by human parvovirus B19 capsid protein VP1.

ABSTRACT: Recent reports demonstrated an association of human parvovirus B19 with inflammatory cardiomyopathy (iCMP), which is accompanied by endothelial dysfunction. As intracellular Ca(2+) activity is a key regulator of cell function and participates in mechanisms leading to endothelial dysfunction, the present experiments explored the effects of the B19 capsid proteins VP1 and VP2. A secreted phospholipase A2 (PLA2)-like activity has been located in the VP1 unique region of the B19 minor capsid protein. As PLA2 has recently been shown to activate the store-operated or capacitative Ca(2+) channel I(CRAC), we analyzed the impact of the viral PLA2 motif on Ca(2+) entry. We cloned the VP1 and VP2 genes isolated from a patient suffering from fatal B19 iCMP into eukaryotic expression vectors. We also generated a B19 replication-competent plasmid to demonstrate PLA2 activity under the control of the complete B19 genome. After the transfection of human endothelial cells (HMEC-1), cytosolic Ca(2+) activity was determined by utilizing Fura-2 fluorescence. VP1 and VP2 expression did not significantly modify basal cytosolic Ca(2+) activity or the decline of cytosolic Ca(2+) activity following the removal of extracellular Ca(2+). However, expression of VP1 and of the full-length B19 clone, but not of VP2, significantly accelerated the increase of cytosolic Ca(2+) activity following the readdition of extracellular Ca(2+) in the presence of thapsigargin, indicating an activation of I(CRAC.) The effect of VP1 was mimicked by the PLA2 product lysophosphatidylcholine and abolished by an inactivating mutation of the PLA2-encoding region of the VP1 gene. Our observations point to the activation of Ca(2+) entry by VP1 PLA2 activity, an effect likely participating in the pathophysiology of B19 infection.

SUBMITTER: Lupescu A

PROVIDER: S-EPMC1642163 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature

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Phospholipase A2 activity-dependent stimulation of Ca2+ entry by human parvovirus B19 capsid protein VP1.

Lupescu Adrian A Bock C-Thomas CT Lang Philipp A PA Aberle Susanne S Kaiser Heike H Kandolf Reinhard R Lang Florian F

Journal of virology 20060906 22

Recent reports demonstrated an association of human parvovirus B19 with inflammatory cardiomyopathy (iCMP), which is accompanied by endothelial dysfunction. As intracellular Ca(2+) activity is a key regulator of cell function and participates in mechanisms leading to endothelial dysfunction, the present experiments explored the effects of the B19 capsid proteins VP1 and VP2. A secreted phospholipase A2 (PLA2)-like activity has been located in the VP1 unique region of the B19 minor capsid protein ...[more]

PMID: 16956939

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Project description:We previously reported in atrial myocytes that inhibition of cAMP-dependent protein kinase (PKA) by laminin (LMN)-integrin signaling activates β2-adrenergic receptor (β2-AR) stimulation of cytosolic phospholipase A2 (cPLA2). The present study sought to determine the signaling mechanisms by which inhibition of PKA activates β2-AR stimulation of cPLA2. We therefore determined the effects of zinterol (0.1 μM; zint-β2-AR) to stimulate ICa,L in atrial myocytes in the absence (+PKA) and presence (-PKA) of the PKA inhibitor (1 μM) KT5720 and compared these results with atrial myocytes attached to laminin (+LMN). Inhibition of Raf-1 (10 μM GW5074), phospholipase C (PLC; 0.5 μM edelfosine), PKC (4 μM chelerythrine) or IP3 receptor (IP3R) signaling (2 μM 2-APB) significantly inhibited zint-β2-AR stimulation of ICa,L in-PKA but not +PKA myocytes. Western blots showed that zint-β2-AR stimulation increased ERK1/2 phosphorylation in-PKA compared to +PKA myocytes. Adenoviral (Adv) expression of dominant negative (dn) -PKCα, dn-Raf-1 or an IP3 affinity trap, each inhibited zint-β2-AR stimulation of ICa,L in + LMN myocytes compared to control +LMN myocytes infected with Adv-βgal. In +LMN myocytes, zint-β2-AR stimulation of ICa,L was enhanced by adenoviral overexpression of wild-type cPLA2 and inhibited by double dn-cPLA2S505A/S515A mutant compared to control +LMN myocytes infected with Adv-βgal. In-PKA myocytes depletion of intracellular Ca2+ stores by 5 μM thapsigargin failed to inhibit zint-β2-AR stimulation of ICa,L via cPLA2. However, disruption of caveolae formation by 10 mM methyl-β-cyclodextrin inhibited zint-β2-AR stimulation of ICa,L in-PKA myocytes significantly more than in +PKA myocytes. We conclude that inhibition of PKA removes inhibition of Raf-1 and thereby allows β2-AR stimulation to act via PKCα/Raf-1/MEK/ERK1/2 and IP3-mediated Ca2+ signaling to stimulate cPLA2 signaling within caveolae. These findings may be relevant to the remodeling of β-AR signaling in failing and/or aging heart, both of which exhibit decreases in adenylate cyclase activity.

Project description:A unique region of human parvovirus B19 virus‑VP1 (B19V‑VP1u) has been linked to a variety of cardiac disorders. However, the precise role of B19V‑VP1u in inducing cardiac injury remains unknown. The present study investigated the effects of B19V‑VP1u and different regions of B19V‑VP1u, including B19V‑VP1uA (residues 1‑60), B19V‑VP1uB (residues 61‑129), B19V‑VP1uC (residues 130‑195) and B19V‑VP1uD (residues 196‑227), on inducing cardiac injury in naïve mice by zymography, immunoblotting, H&E staining and cytokine immunoassay. A significantly higher MMP‑9/MMP‑2 ratio and increased levels of inflammatory cytokines, including IL‑6 and IL‑1β, were detected in the left ventricles of the mice injected with B19V‑non‑structural protein 1 (B19V‑NS1) and B19V‑VP1u, accompanied by increased expression levels of phosphorylated (p‑)ERK and p‑P38. Significantly upregulated expression levels of atrial natriuretic peptide (ANP), heart‑type fatty acid‑binding protein (H‑FABP) and creatine kinase isoenzyme‑MB (CK‑MB), which are well‑known cardiac injury markers, as well as increased infiltration of lymphocytes, were detected in the left ventricles of the mice injected with B19V‑VP1, B19V‑NS1 and B19V‑VP1u. Moreover, a significantly higher MMP‑9/MMP‑2 ratio and increased levels of IL‑6 and IL‑1β were observed in the left ventricles of the mice injected with B19V‑VP1u, B19V‑VP1u‑A, B19V‑VP1u‑B and B19V‑VP1u‑C, accompanied by upregulated p‑ERK and p‑P38 expression. Notably, significantly lower levels of IL‑6 and IL‑1β were observed in the left ventricles of the mice injected with B19V‑VP1uD. Furthermore, significantly increased ANP, H‑FABP and CK‑MB expression levels were detected in the left ventricles of the mice injected with B19V‑VP1u, B19V‑VP1u‑A and B19V‑VP1u‑B, along with enhanced infiltration of lymphocytes. Significantly higher serum IL‑1β, IL‑6, TNF‑α and IFN‑γ levels were also detected in the mice injected with B19V‑VP1u, B19V‑VP1u‑A and B19V‑VP1u‑B. To the best of our knowledge, the findings of the present study were the first to demonstrate that the N‑terminal region (residues 1‑129) of B19V‑VP1u induces an increase in the levels of cardiac injury markers, thus providing evidence for understanding the possible functional regions within B19V‑VP1u.

Dataset Information

Phospholipase A2 activity-dependent stimulation of Ca2+ entry by human parvovirus B19 capsid protein VP1.

Publications

Phospholipase A2 activity-dependent stimulation of Ca2+ entry by human parvovirus B19 capsid protein VP1.

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