Cyclic guanosine monophosphate inhibits the palmitoylation of LETM1 and downregulates the activity of AKT in human pulmonary artery smooth muscle cells

Abstract Cyclic guanosine monophosphate (cGMP) is a drug target for the treatment of pulmonary arterial hypertension (PAH). However, the molecular mechanism of cGMP in the pathogenesis of PAH remains unclear, and long-term use of cGMP target drugs leads to drug resistance. We tried to explore the new targets downstream of cGMP signaling and develop novel therapies for PAH. We combined mass spectrometry (MS)-based quantitative proteomics with click-chemistry-probes to identified palmitoylated candidate proteins. S-palmitoylation assay was ultilized to test whether the palmitoylation level of the candidates were regulated by cGMP. We identified palmitoylated proteins in human pulmonary artery smooth muscle cells (HPASMCs). Functional enrichment of the palmitoylated proteins showed that 52 proteins were involved in transmembrane transport, of which 7 were engaged in mitochondrial transport. S-palmitoylation assay in vitro demonstrated that the inner mitochondrial membrane protein, LETM1, was palmitoylated in the cytoplasmic domain at C-terminus. More importantly, cGMP could inhibit the palmitoylation level of LETM1, which in turn suppressed the activity of AKT regulated by LETM1. Our study found that the palmitoylation of LETM1 was the new target downstream of cGMP signaling. The palmitoylated site of LETM1 may provide a new direction for the development of novel therapies for PAH. Moreover, the palmitoylation level of LEMT1 may be a new biomarker for the analysis of prognosis.