BACKGROUND: The identification and characterization of granule membran
e proteins are becoming increasingly important in understanding the pa
ckaging and secretory function of granules and characterizing diseases
involving granules. A granule membrane protein, granulophysin, has re
cently been identified in the membranes of platelet dense granules, or
ganelles that contain stored ADP, ATP, serotonin, and calcium. Antibod
ies that recognize granulophysin also stain granules of monocytes, neu
trophils, and lymphokine activated killer cells. EXPERIMENTAL DESIGN:
In the present study, the distribution of epitopes recognized by antig
ranulophysin monoclonal antibodies in human tissues was investigated u
sing immunohistochemistry on paraffin sections. Quantitation of the pr
otein was also performed by enzyme-linked immunosorbent assay. The pro
tein was also analyzed in various tissues using Western blotting. RESU
LTS: Granulophysin was localized to the granules of skin melanocytes,
neurons, endocrine gland cells, exocrine glands (except mucin producin
g cells), and surface lining cells. Analysis by Western blots revealed
a typical staining pattern for granulophysin in lung, adrenal gland,
liver, brain, prostate, and pituitary. Atypical bands were present in
the pancreas head (47 kDa) and skeletal muscle (34 kDa). A clear disti
nction was demonstrated between granulophysin and synaptophysin throug
h both immunochemistry and blotting, despite the known cross-reactivit
y of these two proteins. CONCLUSIONS: The findings demonstrate that gr
anulophysin is a widely distributed protein that is frequently associa
ted with granules. We speculate that it may be critical in granule fun
ction.