Sumoylation is crucial for the stability of Leukocyte-specific protein 1 (P5118)

Abstract

Abstract Leukocyte-specific protein 1 (LSP1) is an intracellular protein expressed in leukocytes and endothelial cells and regulates several leukocyte and endothelial cell functions including transmigration and chemotaxis of leukocytes in inflammation. There is a discrepancy between its predicted molecular weight (≈37KDa) and that detected in SDS-PAGE (52KDa). To solve this discrepancy, we tested the hypothesis that LSP1 is sumoylated immediately after its translation. Here we demonstrate that, in transfected cells, SUMO1 is conjugated to LSP1 and Ubc9 acts as a SUMO1 ligase for LSP1. Moreover, the sumoylated LSP1 can be desumoylated by the over-expression of SENP1, a SUMO-specific protease. Single lysine to alanine mutation at lysine residue 270 or 318 of recombinant mouse LSP1 prevented its sumoylation in vitro. These LSP1 mutants were degraded rapidly compared to their wild type counterpart. Our results show that sumoylation enhances LSP1 stability, which may ensure its functions in leukocytes and endothelial cells.