The neurotoxic secreted phospholipase A2 from the Vipera a. ammodytes venom targets cytochrome c oxidase in neuronal mitochondria

Abstract

The β-neurotoxic secreted phospholipases A2 (sPLA2s) block neuro-muscular transmission by poisoning nerve terminals. Damage inflicted by such sPLA2s (β-ntx) on neuronal mitochondria is characteristic, very similar to that induced by structurally homologous endogenous group IIA sPLA2 when its activity is elevated, as, for example, in the early phase of Alzheimer’s disease. Using ammodytoxin (Atx), the β-ntx from the venom of the nose-horned viper (Vipera a. ammodytes), the sPLA2 receptor R25 has been detected in neuronal mitochondria. This receptor has been purified from porcine cerebral cortex mitochondria by a new Atx-affinity-based chromatographic procedure. Mass spectrometry analysis revealed R25 to be the subunit II of cytochrome c oxidase (CCOX), an essential constituent of the respiratory chain complex. CCOX was confirmed as being the first intracellular membrane receptor for sPLA2 by alternative Atx-affinity-labellings of purified CCOX, supported also by the encounter of Atx and CCOX in PC12 cells. This discovery suggests the explanation of the mechanism by which β-ntx hinders production of ATP in poisoned nerve endings. It also provides a new insight into the potential function and dysfunction of endogenous GIIA sPLA2 in mitochondria.

Secreted Phospholipases A2 - not just Enzymes: Revisited

“…The structural diversity of sPLA 2 -BPs is consistent with the wide range of pathophysiological activities that have been associated with sPLA 2 s. By binding to sPLA 2 -BPs, sPLA 2 s have been suggested to be involved in inflammation [64,65], hormone release [66,67], neurotoxicity [20,37,68,69] and myotoxicity [22]. It has already been confirmed that sPLA 2 s are ligands for specific sPLA 2 -BPs in cytokine production [70], cell proliferation [71][72][73], cell migration [74], lipid mediator production [75], antibacterial activity [73] and blood coagulation [40].…”

“…(2) heparan sulphate proteoglycans (HSPGs); (3) integrins; (4) vascular endothelial growth factor receptors (VEGFRs); and (5) ion channels. Two new integral membrane sPLA 2 -BPs have been described recently, a G-protein-coupled receptor (GPCR), and cytochrome c oxidase (CCOX) [35,37]. CCOX is the only known intracellular membrane sPLA 2 -BP, as all of the other integral membrane sPLA 2 -BPs are located in the plasma membrane.…”

“…CCOX is an essential constituent of the respiratory chain complex, and was characterized as an sPLA2-BP due to its binding to Atx [37]. Through binding to subunit II, Atx was shown to inhibit the oxidase activity of CCOX, independent of its phospholipase activity.…”

Crystal Structure of Isoform CBd of the Basic Phospholipase A2 Subunit of Crotoxin: Description of the Structural Framework of CB for Interaction with Protein Targets

“…According to this hypothesis, tetrameric or dimeric configurations may play an important role in neurotoxicity or other functions of human inflammatory sPLA 2 GIIA. Moreover, in pathological conditions, where high concentrations of sPLA 2 have been detected [ 41 , 42 , 43 ], formation of sPLA 2 oligomers could be expected. Additional in vivo studies are needed to explain the role of oligomerization of sPLA 2 in pathophysiological processes.…”

Short Linear Motifs Characterizing Snake Venom and Mammalian Phospholipases A2

“…We searched the SLiMs present in the ELM resource [24] and conserved in the different groups of sPLA2s. We selected for the search "all cellular compartments" because sPLA2s are internalized in cells, and were observed to localize in different cellular organelles, in vesicles in the cytoplasm, in mitochondria, and in the nucleus [26][27][28][29][30]. Of all the motifs identified (Table S1A,B, Supplementary Material), we selected those conserved in toxins but not in mammalian PLA2s, or vice versa.…”