MOLECULAR CHARACTERIZATION OF THE SIGNAL RESPONSIBLE FOR THE TARGETING OF THE INTERLEUKIN-2 RECEPTOR-BETA CHAIN TOWARD INTRACELLULAR DEGRADATION

During receptor-mediated endocytosis, most growth factor receptors are transported to late endocytic compartments and degraded. This process is important to control their expression on the cell surface and requ ires sorting in early endocytic compartments. Little is known about th e mechanisms and the signals involved. We have studied the signal invo lved in targeting the interleukin 2 receptor beta chain (IL2R beta), a member of the cytokine receptor superfamily, toward degradation after internalization. We show that a motif of 8 amino acids in the cytosol ic tail of IL2R beta is sufficient to target a normally recycling rece ptor toward degradation. Deletion of this signal strongly impairs IL2R beta degradation. Further molecular characterization of the motif sho ws that it does not resemble the well documented tyrosine and dileucin e families of trafficking signals.