MOSCAT: Aldehyde-Selective Chemical Proteomics for Site-Specific Profiling of Cinnamaldehyde Targets in Living Cells

Cinnamaldehyde (CA), a bioactive compound from cinnamon,
exhibits
diverse pharmacological activities including anti-inflammatory and
anticancer effects. However, comprehensive exploration of the target
landscape of CA at site-specific resolution remains challenging. Herein,
we developed MOSCAT (MethOxyamine-enabled Site-specific Cinnamaldehyde
Tagging), a probe-free chemical proteomic strategy for mapping cinnamaldehyde-targeted
proteins in living cells. Unlike existing probe-based approaches requiring
synthetic CA derivatives, MOSCAT directly captures native CA-protein
adducts by exploiting the intrinsic aldehyde functionality of CA,
providing unbiased target profiling with residue-level resolution.
Using MOSCAT, we identified 632 CA-modification sites across 480 proteins
in human cells. Remarkably, over 70% of these sites overlap with other
post-translational modifications, particularly S-nitrosylation and
S-sulfenylation, revealing mechanistic links to the anti-inflammatory
activity of CA. Notably, we discovered that CA covalently modifies
Cys93 of GPX4, a conserved residue critical for ferroptosis regulation.
This modification triggers proteasome-mediated GPX4 degradation, identifying
a specific covalent engagement site associated with CA-induced ferroptosis.
Our findings demonstrate MOSCAT as a powerful platform for elucidating
molecular mechanisms of electrophilic natural products and highlight
GPX4 Cys93 as a promising druggable site for CA-based therapeutic
interventions.