Final answer:
After protease treatment, the GFP attached to the CD2 protein would remain on the cell exterior as only the intracellular domain is cleaved off. Proteins synthesized in the ER lumen end up on the cell's exterior after exocytosis. Limited endocytosis with normal exocytosis in a cell would lead to increased plasma membrane size.
Step-by-step explanation:
When CD2 is fused to green fluorescent protein (GFP) with the GFP on the extracellular side of the membrane and a protease that cleaves the protein between the end of its transmembrane domain and its intracellular domain is added to the cytoplasm, one would expect to see the GFP remain on the outside of the cell, since the extracellular domain is not affected by the protease in the cytoplasm. The fluorescence microscope would reveal the extracellular GFP still intact and fluorescent on the cell surface, as the proteolytic cleavage has occurred on the cytoplasmic side, releasing only the intracellular segment of the protein.
Peripheral membrane proteins synthesized in the lumen of the ER would end up on the outside of the plasma membrane following the secretory pathway. During this process, the protein moves through the ER and the Golgi apparatus before being transported in vesicles that fuse with the cell's plasma membrane, depositing the protein on the outside of the cell. In a cell that can perform exocytosis but only minimal endocytosis, the consequences would involve secretion of intracellular proteins and a gradual increase in plasma membrane size, potentially affecting cell homeostasis and balance between material intake and release.