title: 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.
authors.affiliation: Physiologisches Institut, der Universität Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany.
authors.forename: Adrian
authors.initials: A
authors.lastname: Lupescu
authors.forename: C-Thomas
authors.initials: CT
authors.lastname: Bock
authors.forename: Philipp A
authors.initials: PA
authors.lastname: Lang
authors.forename: Susanne
authors.initials: S
authors.lastname: Aberle
authors.forename: Heike
authors.initials: H
authors.lastname: Kaiser
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kandolf
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D002118:Calcium / Q000378:metabolism*; D036022:Capsid Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000737:chemistry; D042783:Endothelial Cells / Q000821:virology; D005453:Fluorescence; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D016732:Parvovirus B19, Human / Q000235:genetics / Q000502:physiology*; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism*; D054467:Phospholipases A2; D013194:Staining and Labeling; D014162:Transfection
chemical_list: D036022:Capsid Proteins; C095547:capsid protein VP1, parvovirus B19; C095548:capsid protein VP2, parvovirus B19; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium; D016257:Fura-2