The VP1 capsid protein of adeno-associated virus type 2 is carrying a phospholipase A2 domain required for virus infectivity

Sequence analysis revealed phospholipase A2 (PLA2) motifs in capsid proteins of parvoviruses. Although PLA2 activity is not known to exist in viruses, putative PLA2s from divergent parvoviruses, human B19, porcine parvovirus, and insect GmDNV (densovirus from Galleria mellonella), can emulate catalytic properties of secreted PLA2. Mutations of critical amino acids strongly reduce both PLA2 activity and, proportionally, viral infectivity, but cell surface attachment, entry, and endocytosis by PLA2-deficient virions are not affected. PLA2 activity is critical for efficient transfer of the viral genome from late endosomes/lysosomes to the nucleus to initiate replication. These findings offer the prospect of developing PLA2 inhibitors as a new class of antiviral drugs against parvovirus infections and associated diseases.

In recent years, there has been great interest in the study of phospholipid metabolism in intact cell systems. Such an interest arises mainly from the discovery that cellular membrane phospholipids serve not only in structural roles, but are also reservoirs of preformed second messenger molecules with key roles in cellular signaling. These second messenger molecules are generated by agonist-induced activation and secretion of intracellular and extracellular phospholipases, respectively, i.e. enzymes that cleave ester bonds within phospholipids. Prominent members of the large collection of signal-activated phospholipases are the phospholipase A2s. These enzymes hydrolyze the sn-2 ester bond of phospholipids, releasing a free fatty acid and a lysophospholipid, both of which may alter cell function. In addition to its role in cellular signaling, phospholipase A2 has recently been recognized to be involved in a wide number of pathophysiological situations, ranging from systemic and acute inflammatory conditions to cancer. A growing number of pharmacologic inhibitors will help define the role of particular phospholipase A2s in signaling cascades.