WIDE DISTRIBUTION OF GRANULOPHYSIN EPITOPES IN GRANULES OF HUMAN TISSUES

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.