The Unconventional Role of ABHD17A in Increasing the S-Palmitoylation and Antiviral Activity of IFITM1 by Downregulating ABHD16A.

The broad-spectrum antiviral functions of interferon-inducible transmembrane 1 (IFITM1) rely on S-palmitoylation post-translational modification. α/β-hydrolase domain-containing 17A (ABHD17A) has been reported to be responsible for protein depalmitoylation over the past decade, but whether and how ABHD17A regulates the dynamic S-palmitoylation modification of IFITM1 remains unknown. Here, we demonstrated that ABHD17A physically interacts with IFITM1 and increases the S-palmitoylation level of IFITM1. Sequence alignment revealed that ABHD17A lacked the DHHC motif, which is capable of catalyzing the S-palmitoylation modification. Thus, we screened multiple candidate palmitoylating and depalmitoylating enzymes that may contribute to ABHD17A-induced upregulation of IFITM1 S-palmitoylation. The recently discovered depalmitoylase ABHD16A was significantly downregulated by ABHD17A, which counteracted the palmitate-removing reactions of ABHD16A on IFITM1 and subsequently upregulated the S-palmitoylation level and antiviral activity of IFITM1. Our work therefore elucidated the unconventional role of depalmitoylase ABHD17A in elevating the S-palmitoylation modification, expanded the biological functions of ABHD17A in innate immunity, and provided potential targets for viral disease therapy.