Degradation Of Membrane Receptors Research Articles

EGF Uptake and Degradation Assay to Determine the Effect of HTLV Regulatory Proteins on the ESCRT-Dependent MVB Pathway.

The endosomal sorting complex required for transport (ESCRT) pathway plays key roles in multivesicular bodies (MVBs) formation and lysosomal degradation of membrane receptors, viral budding, and midbody abscission during cytokinesis. The epidermal growth factor receptor (EGFR) is regarded as a prototypical cargo of the MVB/ESCRT pathway and following stimulation by epidermal growth factor (EGF) EGFR/EGF complexes are internalized, sorted into MVBs, and degraded by lysosomes or recycled back to the cell membrane. Here, we describe an assay to analyze the effect of human T-cell leukemia (HTLV) regulatory proteins on the functionality of ESCRT-dependent MVB/lysosomal trafficking of EGFR/EGF complexes. This is performed by direct visualization and quantification of the rate of EGF-Alexa595/EGFR internalization and degradation in HeLa cells expressing HTLV regulatory proteins by immunofluorescence and western blot.

Endocytosis and Trafficking of Natriuretic Peptide Receptor-A: Potential Role of Short Sequence Motifs.

The targeted endocytosis and redistribution of transmembrane receptors among membrane-bound subcellular organelles are vital for their correct signaling and physiological functions. Membrane receptors committed for internalization and trafficking pathways are sorted into coated vesicles. Cardiac hormones, atrial and brain natriuretic peptides (ANP and BNP) bind to guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) and elicit the generation of intracellular second messenger cyclic guanosine 3',5'-monophosphate (cGMP), which lowers blood pressure and incidence of heart failure. After ligand binding, the receptor is rapidly internalized, sequestrated, and redistributed into intracellular locations. Thus, NPRA is considered a dynamic cellular macromolecule that traverses different subcellular locations through its lifetime. The utilization of pharmacologic and molecular perturbants has helped in delineating the pathways of endocytosis, trafficking, down-regulation, and degradation of membrane receptors in intact cells. This review describes the investigation of the mechanisms of internalization, trafficking, and redistribution of NPRA compared with other cell surface receptors from the plasma membrane into the cell interior. The roles of different short-signal peptide sequence motifs in the internalization and trafficking of other membrane receptors have been briefly reviewed and their potential significance in the internalization and trafficking of NPRA is discussed.

A VAST staging area for regulatory proteins

The vesicle trafficking system has long been known to influence signal transduction through its role in biogenesis and degradation of membrane receptors (1). There are also well known examples of vesicle-associated regulatory proteins, such as Ire1 and SREBP, that control responses closely tied to vesicle properties or function (2, 3). But a new paradigm is emerging, as illustrated by a study in this issue of PNAS (4), in which vesicle-associated signal transduction (VAST) may not be related to trafficking of a transmembrane receptor. Rather, vesicles serve as staging areas for regulatory proteins, facilitating interactions that ultimately lead to activation or effector interaction (Fig. 1).