Abstract
Induction of surface Mac-1 by inflammatory stimuli is fundamental to a broad spectrum of granulocyte adherence reactions. To study the mechanisms regulating expression and intracellular translocation of Mac-1, neutrophils were disrupted by nitrogen cavitation and subcellular organelles were isolated on Percoll gradients. Mac-1 was visualized by a sensitive Western Blot Assay made quantitative by digital imaging. Unstimulated neutrophils contained 29%, 27% and 26% of total (5.60 μg/107 cells) Mac-1 in beta (1.10 g/ml density granules) pre-gamma (1.07 g/ml density granules) and gamma (plasma membrane) fractions, respectively. fMLP elicited a ≥50% translocation of Mac-1 in the pre-gamma to the gamma fraction but no translocation of Mac-1 from the beta fraction and a ≤5% release of vitamin B12 transport protein. In contrast, PMA (1μg/ml) stimulation resulted in a ≥50% decrease in both the beta and pre-gamma Mac-1 pools concomitant with an increase in the gamma fraction and, a ≥50% release of vitamin B12 transport protein. Under both conditions, a 4-7 fold increase of surface Mac-1 was detectable by flow cytofluorography. Among both control and stimulated neutrophil suspensions, only 5% and 20% of Mac-1 partitioned with Triton-X 114 in beta and gamma fractions, respectively. These findings indicate that Mac-1 is contained in multiple distinct intracellular pools, and that it may exist both as an integral membrane protein and in other forms. Its “up regulation” by chemotactic factors is associated with a recruitment of a pre-gamma granular pool but does not require the participation of the beta fraction associated Mac-1 pool.
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Jones, D., Anderson, D., Burr, B. et al. SUBCELLULAR LOCATION OF MAC-1 (CR-3) IN HUMAN NEUTROPHILS: EFFECTS OF CHEMOTACTIC FACTORS AND PMA. Pediatr Res 21 (Suppl 4), 312 (1987). https://doi.org/10.1203/00006450-198704010-00872
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DOI: https://doi.org/10.1203/00006450-198704010-00872