The clickable activity-based probe of anti-apoptotic calenduloside E

Abstract

Context: Calenduloside E (CE), one of the primary natural products found in Aralia elata (Miq.) Seem. (Araliaceae), possesses prominent anti-apoptotic potential. A previous study found that one of the anti-apoptotic CE targets is heat shock protein 90 AB1 (Hsp90AB1) by probe CE-P, while the other targets of CE still need to be identified with more efficient probes.

Objective: This study investigates CE analogue (CEA) as one clickable activity-based probe for use in exploring anti-apoptotic CE targets.

Materials and methods: Pretreatment of HUVECs with CEA (1.25 μM) for 8 hr, followed by ox-LDL stimulation for 24 h. Flow cytometry analysis and JC-1 staining assays were performed The kinetic constant measurements were tested by the Biacore T200, CM5 Sensor Chip which was activated by using sulpho-NHS/EDC. Ligands were dissolved and injected with a concentration of 12.5, 6.25, 3.125, 1.56, 0.78 and 0 μM.

Results: CEA was confirmed to possess an anti-apoptotic effect. The probable targets of CE/CEA were calculated, and as one of the higher scores proteins (Fit values: 0.88/0.86), Hsp90 properly got our attention. Molecular modelling study showed that both CE and CEA could bind to Hsp90 with the similar interaction, and the docking scores (S value) were −7.61 and −7.33. SPR assay provided more evidence to prove that CEA can interact with Hsp90 with the KD value 11.7 µM.

Discussion and conclusions: Our results suggest that clickable probe CEA could alleviate ox-LDL induced apoptosis by a similar mechanism of anti-apoptotic CE, and afforded the possibility of identifying additional anti-apoptotic targets of CE.

Keywords:

• Aralia elata
• natural products
• CE analogue
• molecular modelling
• SPR
• Hsp90

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Natural Sciences Foundation of Beijing [Grant No. 7144225], the National Natural Sciences Foundation of China [Grant No. 81302656 and 81502929], the National Science and Technology Major Project [Grant No. 2015ZX09501004-001-003], and the CAMS Innovation Fund for Medical Science (CIFMS) [Grant No. 2016-I2M-1-012].