Implication of annexin 1 in phagocytosis: effects of n-terminal domain deletions and point mutations of the phosphorylation site Ser-27.

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. Copyright 2001 Academic Press.