Western blotting analyses of G-CSFR in placental membrane indicated that placental G-CSFR protein expression is modulated according to gestational age and coincides with changes in G-CSFR mRNA levels. These data suggest that expression of G-CSFR at the materno-fetal interface may be subject to transcriptional regulation. The ratio of the two distinct 120-kDa and 150-kDa G-CSFR proteins detected by Western blotting analysis changed with gestation. Both G-CSFR molecules have equal affinity for G-CSF. Nine possible A-glycosylation sites exist in G-CSFR, most on the extracellular domain, and the 120-kDa molecule may thus be a lesser glycosylated form of the 150-kDa molecule. buy cipro
Alternatively, it may be a proteolytic fragment of the 150-kDa molecule as described by others. Affinity cross-linking experiments have shown that a 150-kDa G-CSFR is expressed on human neutrophilic granulocytes, and three G-CSFR molecules of 145, 135, and 115 kDa have been detected by Western blotting of a human, G-CSF-responsive monocytic leukemic cell line. Thus the 120-kDa G-CSFR may be specific to placental tissue. Although it is not known whether the structural differences in G-CSFR molecules affect receptor function, the fact that the larger form of G-CSFR is highest in third-trimester placental tissues may reflect a functional difference between first- and third-trimester placental G-CSFR.