Catalytically inactive phospholipase A2 homologue binds to vascular endothelial growth factor receptor-2 via a C-terminal loop region

Abstract

VEGF (vascular endothelial growth factor) regulates neovascularization through binding to its receptor KDR (kinase insert domain-containing receptor; VEGF receptor-2). We recently identified a catalytically inactive PLA(2) (phospholipase A(2)) homologue (KDR-bp) in the venom of eastern cottonmouth (Agkistrodon piscivorus piscivorus) as a third KDR-binding protein, in addition to VEGF(165) and tissue inhibitor of metalloproteinase-3. KDR-bp binds to the extracellular domain of KDR with a K(d) of 10(-8) M, resulting in specific blockade of endothelial cell growth induced by VEGF(165). Inactive PLA(2) homologues are widely distributed in the venoms of Viperidae snakes and are known to act as myotoxins. In the present study, we demonstrated that KDR-binding ability is a common characteristic for inactive PLA(2) homologues in snake venom, but not for active PLA(2)s such as neurotoxic and platelet aggregation-modulating PLA(2)s. To understand better the KDR and KDR-bp interaction, we resolved the binding region of KDR-bp using eight synthetic peptides designed based on the structure of KDR-bp. A synthetic peptide based on the structure of the C-terminal loop region of KDR-bp showed high affinity for KDR, but other peptides did not, suggesting that the C-terminal loop region of KDR-bp is involved in the interaction with KDR. The results of the present study provide insight into the binding of inactive PLA(2) homologues to KDR, and may also assist in the design of novel anti-KDR molecules for anti-angiogenic therapy.

Cellular pathology induced by snake venom phospholipase A2 myotoxins and neurotoxins: common aspects of their mechanisms of action

“…The recent finding of strong and specific binding of Lys49 PLA 2 s to the VEGF receptor is intriguing, but the possible significance of this interaction in myotoxicity is unkown [40]. It is noteworthy, however, that binding of Lys49 PLA 2 s to this receptor occurs through the C-terminal region, known to play a key role in plasma membrane perturbation [41]. It has been observed that negatively-charged lipids in the plasma membrane may play a role in the binding of some locally-acting myotoxic PLA 2 s [42].…”

Non-enzymatic proteins from snake venoms: A gold mine of pharmacological tools and drug leads

“…We were able to find, isolate and characterize a new type of VEGF, named vammin, from the venom of V. ammodytes ammodytes, and VR-1 from the venom of D. russelli russelli (formerly Vipera russelli russelli) (Yamazaki et al, 2003) and several other snake venoms (Yamazaki et al, 2010). From the initial inspiration from the paper of HF (Komori et al, 1999), we got many interesting results (Fujiwara et al, 2008;Matsunaga et al, 2009;Suto et al, 2005;Tokunaga et al, 2005Tokunaga et al, , 2006Yamazaki et al, 2003Yamazaki et al, , 2005a2010;Yamazaki and Morita, 2006) and enjoyed our work on snake venom-derived VEGFs as a new subject with my colleagues and graduate students. …”

Calcium imaging of muscle cells treated with snake myotoxins reveals toxin synergism and presence of acceptors

“…Even less is known on the cell binding step of myotoxic PLA2 s, which is clearly essential for the display of their toxicity [14]. Receptors for myotoxins isolated from the venom of Oxyuranus scutellatus have been identified [15,16] and it has been suggested that the receptor of the Lys49 myotoxin is the VEGF (vascular endothelial growth factor) receptor itself [17,18]. The presence of specific plasma membrane receptors is also supported by the selectivity of some myotoxins for type I muscle fibers [19,20].…”