Group V Secretory Phospholipase A2 Regulates Endocytosis of Acetylated LDL by Transcriptional Activation of PGK1 in RAW264.7 Macrophage Cell Line

• Published in: Journal of Atherosclerosis and Thrombosis Vol. 29; no. 5; pp. 692 - 718
• Main Authors: Fujioka, Daisuke, Watanabe, Yosuke, Nakamura, Takamitsu, Yokoyama, Takashi, Miyazawa, Keiji, Murakami, Makoto, Kugiyama, Kiyotaka
• Format: Journal Article
• Language: English
• Published: Japan Atherosclerosis Society 01.05.2022
• Subjects: Actin polymerization; Endocytosis; Group V secretory phospholipase A2; Macrophage; Original; Phosphoglycerate kinase 1
• ISSN: 1340-3478; 1880-3873
• DOI: 10.5551/jat.62216

Aims: It was suggested that group V secretory phospholipase A2 (sPLA2-V) existed in the nucleus. This study examined whether nuclear sPLA2-V plays a role in endocytosis of acetylated low-density lipoprotein (AcLDL) in monocyte/macrophage-like cell line RAW264.7 cells.Methods: RAW264.7 cells were transfected with shRNA vector targeting sPLA2-V (sPLA2-V-knockdown [KD] cells) or empty vector (sPLA2-V-wild-type [WT] cells). AcLDL endocytosis was assessed by incubation with 125I-AcLDL or AcLDL conjugated with pHrodo. Actin polymerization was assessed by flow cytometry using Alexa Fluor 546-phalloidin.Results: In immunofluorescence microscopic studies, sPLA2-V was detected in the nucleus. ChIP-Seq and ChIP-qPCR analyses showed binding of sPLA2-V to the promoter region of the phosphoglycerate kinase 1 (Pgk1) gene. In the promoter assay, sPLA2-V-KD cells had lower promoter activity of the Pgk1 gene than sPLA2-V-WT cells, and this decrease could be reversed by transfection with a vector encoding sPLA2-V-H48Q that lacks enzymatic activity. Compared with sPLA2-V-WT cells, sPLA2-V-KD cells had decreased PGK1 protein expression, beclin 1 (Beclin1) phosphorylation at S30, and class III PI3-kinase activity that could also be restored by transfection with sPLA2-V-H48Q. sPLA2-V-KD cells had impaired actin polymerization and endocytosis, which was reversed by introduction of sPLA2-V-H48Q or PGK1 overexpression. In sPLA2-V-WT cells, siRNA-mediated depletion of PGK1 suppressed Beclin1 phosphorylation and impaired actin polymerization and intracellular trafficking of pHrodo-conjugated AcLDL.Conclusions: Nuclear sPLA2-V binds to the Pgk1 gene promoter region and increases its transcriptional activity. sPLA2-V regulates AcLDL endocytosis through PGK1-Beclin1 in a manner that is independent of its enzymatic activity in RAW264.7 cells.