The Inactivation Mechanism of Human Group IIA Phospholipase A₂ by Scalaradial

Abstract

Secretory phospholipases A(2) (sPLA(2)s) are implicated in the pathogenesis of several inflammation diseases, such as rheumatoid arthritis, septic shock, psoriasis, and asthma. Thus, an understanding of their inactivation mechanisms could be useful for the development of new classes of chemical selective inhibitors. In the marine environment, several bioactive terpenoids possess interesting anti-inflammatory activity, often through covalent and/or noncovalent inactivation of sPLA(2). Herein, we report the molecular mechanism of human group IIA phospholipase A(2) (sPLA(2)-IIA) inactivation by Scalaradial (SLD), a marine 1,4-dialdehyde terpenoid isolated from the sponge Cacospongia mollior and endowed with a significant anti-inflammatory profile. Our results have been collected by a combination of biochemical approaches, advanced mass spectrometry, surface plasmon resonance, and molecular modeling. These suggest that SLD acts as a competitive inhibitor. Indeed, the sPLA(2)-IIA inactivation process seems to be driven by the noncovalent recognition process of SLD in the enzyme active site and by chelation of the catalytic calcium ion. In contrast, covalent modification of the enzyme by the SLD dialdehyde moiety emerges as only a minor side event in the ligand-enzyme interaction. These results could be helpful for the rational design of new PLA(2) inhibitors that would be able to selectively target the enzyme active site.

Marine natural products

“…Both showed modest growth inhibition against human colon cancer cell lines, 720 The archetypical anti-inammatory scalarane sesterterpenoid scalaradial (Cacospongia mollior) 722 acted as a non-covalent binder in the active site of phospholipase A 2 and chelates Ca 2+ but did not covalently bind to the enzyme through dial reactivity. 723 The total synthesis of solomonsterol B (Theonella swinhoei) 724 has allowed for SAR studies to be performed. 725 Chalinulasterol 863 came from Chalinula molitba (Little San Salvador, Caribbean) and is the rst chlorinated/sulfated sterol known.…”

Scalarane sesterterpenes from Thorectidae sponges as inhibitors of TDP-43 nuclear factor

“…The finding of scalarane derivatives in nudibranchs 3 could be ascribed to their dietary origin. Members of the family have been found to possess a wide range of biological activities including cytotoxic, 4 enzyme inhibitory activity [5][6][7] and farnesoid X receptor (FXR) antagonistic activities. 8 In particular, heteronemin, 9 often found as a major component of the reported sponges, was found to possess remarkable pharmacological activity.…”

In cell scalaradial interactome profiling using a bio-orthogonal clickable probe

“…In this paper, we employed the copper-(I)-catalyzed variant of the Huisgen 1,3-dipolar cycloaddition, a straightforward reaction leading to a stable 1,2,3-triazole adduct through the reaction of azides and terminal alkynes, 12 to guide the in cell identification of the protein targets of Scalaradial (SLD), a natural scalarane sesterterpenoid isolated from the sponge Cacospongia mollior. 13 SLD has been reported to inhibit PLA 2 activity, 14,15 EGF-stimulated Akt phosphorylation and NF-kB activation, causing cell death by inducing apoptosis. [16][17][18] Thus, we selected this interesting natural product for its relevant antiinflammatory profile as a probe for a comparative analysis between in vitro and in vivo chemical proteomics procedures, aiming to a rational validation of the two techniques along with the discovery of new SLD targets responsible for its remarkable pharmacological activity.…”

“…S1, ESI †). On the basis of the MS and MS/MS spectra and our previously published data, 14,15,21 a reaction mechanism was proposed, based on the formation of a Schiff base intermediate by reaction of the TRX-Az terminal amino group and one of the SLD aldehyde carbonyls, followed by a cyclization step whose product evolved to a pyrrole species (Fig. 2).…”

“…6). In spite of the large number of potential hits, often due to a high background content possibly derived to the nonspecific binding of abundant proteins, 25 our attention was focused on a large protein sub-network accounting for the SLD reported pharmacological profile, [14][15][16][17][18] in which PRXs with several 14-3-3 isoforms and the proteasome machinery complex are strictly connected. The recovery of PRX-1 and 14-3-3, common hits of the in vitro proteomic analysis, represented a validation for the in cell procedure, and in addition the proteasome was found as a formerly undetected SLD target.…”