SORTING OF THE SPECIFIC GRANULE PROTEIN, NGAL, DURING GRANULOCYTIC MATURATION OF HL-60 CELLS

The different types of human neutrophil granules (azurophil, specific, and gelatinase granules) are formed sequentially during maturation of neutrophils from the promyelocyte stage to the band cell stage, The p romyelocytic HL-60 cells can maturate to segmented granulocytes but ar e incapable of activating the transcription of any known intragranular protein, normally located in specific or gelatinase granules, To stud y the sorting of granule proteins during maturation, we transfected HL -60 cells with the specific granule protein NGAL, inserted under contr ol of a cytomegalovirus promoter. We previously showed that NGAL is so rted to azurophil granules and colocalizes with myeloperoxidase in und ifferentiated HL-60 cells. We show here that, when such transfected HL -60 cells differentiate into granulocytes, newly synthesized NGAL is n ot retained in granules but is constitutively secreted, This indicates that highly specific mechanisms must exist that are responsible for d iverting transport vesicles into storage granules, and that HL-60 cell s not only lack the ability to activate transcription of specific gran ule proteins, but also lose the ability to form storage granules durin g maturation. (C) 1997 by The American Society of Hematology.