although the smaller csf-1 precursor specified by the 1.6-kb human cdna was stably expressed as a membrane-bound glycoprotein at the cell surface and was slowly cleaved to release the extracellular growth factor , the cell-associated product of the 4-kb clone was efficiently processed to the secreted form and was not detected on the plasma membrane .
C0699040
cell surface
C0007634
the cell