AN INVESTIGATION OF THE NUCLEAR LIPID ASSOCIATED PROMYELOCYTIC LEUKEMIA (PML) STRUCTURES (LAPS) PROTEOME USING BIOTIN PROXIMITY LABELLING

Abstract

Fatty acids are stored in triacyl glycerides or cholesterol esters in lipid droplets (LDs). While most LDs are cytoplasmic, there are also nuclear lipid droplets (nLDs) that associate with promyelocytic leukemia (PML) called Lipid Associated PML Structures (LAPS). The protein composition of LAPS is distinct from PML nuclear bodies but the complete LAPS proteome has not been characterized. To address this, APEX2 proximity labelling was used to identify proteins that interact with LAPS. Using this approach, protein mitogen-activated protein kinase-activated protein kinase 2 (MK2) was identified as a high confidence interactor. Immunofluorescence confocal microscopy showed that two MK2 isoforms associated with LAPS. When the kinase activity of MK2 was inhibited, there was an increase in LAPS/cell. While oleate treatment had an inconsequential effect on the p38 signaling cascade, this pathway was severely dysregulation in PML-deficient U2OS cells. In conclusion, MK2 was identified and validated as a LAPS-interacting kinase.