IMPLICATION OF ANNEXIN 1 IN PHAGOCYTOSIS: EFFECTS OF N‐TERMINAL DOMAIN DELETIONS AND POINT MUTATIONS OF THE PHOSPHORYLATION SITE SER‐27

Abstract

Directed mutagenesis, in the form of deletions and point mutations, was used to investigate the regulatory importance of the N-terminal domain of annexin 1. Wild-type and mutant forms were fused to green fluorescent protein (GFP) to track their localization and introduced in to J-774A.1 cells by transfection. The fusion of annexin 1 to GFP at the N- or C-terminal end did not alter the cellular distribution or co-localization with phagosomes. The effects of mutations were determined according to these characteristics. The prominent effect resulted from S27E mutation which mimics the phosphorylated state of Ser-27. Although still retaining the granular structures in the cytoplasm, S27E annexin 1 failed to associate with the phagosomal protein complex. This suggests an essential regulatory role of the phosphorylation of residue 27 in annexin 1 function.