Discovery of a Natural Small-Molecule Inhibitor to Novel Target STAT5A for Ischemic Stroke Therapy

Signal transducer and activator of transcription 5A (STAT5A) is known to regulate the processes of various cancers but remains unexplored in neuroprotective effects, especially in ischemic stroke (IS). Based on an HPLC-DAD-HRESIMS-oriented strategy, 16 stilbenoid dimers [(+)-<b>1</b>/(-)-<b>1</b> - (+)-<b>9</b>/(-)-<b>9</b>] were isolated from <i>Heterosmilax yunnanensis</i> (Liliaceae). Pharmacological evaluations showed that (±)-<b>2</b> could remarkably alleviate neuronal ischemic damage in MCAO models. A four-step synthesis of (±)-<b>2</b> was achieved in a stereo- and regioselective manner by a protecting-group-free strategy. The SAR analysis indicated the necessity of two hydroxy groups at C-3/C-4 or C-3/C-5 in the A ring. Using a chemoproteomics technology, STAT5A was identified as the direct cellular target of (±)-<b>2</b>. Mechanistically, (±)-<b>2</b> conjugates with STAT5A by the key Lys644 residue to inhibit its phosphorylation, thus exerting anti-IS effects. Our findings demonstrate that STAT5A might be a novel target for IS therapy, and (±)-<b>2</b> was the first natural anti-IS drug candidate targeting STAT5A.