Fig. 7.

Model for CSF-1R endocytosis and trafficking to macropinosomes. Ligated CSF-1R stimulates the production of macropinosomes as it is internalized by small vesicle endocytosis. CME endosomes undergo homotypic fusion before trafficking to Rab5-positive macropinosomes. Macropinosomes mature into Rab7-positive late endosomes, whereupon the receptor is delivered to their lumen. The CSF-1R is finally degraded ∼45 min after expose to CSF-1. This model indicates that macropinosomes serve as a site of MVB biogenesis.