The modification of cytosolic proteins with polyubiquitin chains targets them for recognition and degradation by the multisubunit proteolytic particle, the 26S proteasome. Membrane proteins are also substrates for ubiquitination. Integral membrane proteins of the endoplasmic reticulum are ubiquitinated and destroyed by the proteasome. However, it has been shown recently that the ubiquitination of @entity375 plasma membrane proteins signals their degradation by the proteolytic system in the lysosome-like vacuole. Ubiquitination of several different classes of cell surface proteins serves as a signal for their entry into the endocytic pathway; this leads to their transport to the vacuole, where they are permanently inactivated by degradation. In @entity375 , @entity8290 has been implicated as an internalization signal for most, if not all, endogenous plasma membrane proteins that are known to be endocytosed. @entity8290 -dependent internalization has been best characterized for two proteins: the mating pheromone alpha-factor receptor and the @entity5537 permease. Some @entity1 cell surface receptors are also ubiquitinated at the plasma membrane. Ubiquitination machinery is required for ligand-induced endocytosis of the growth hormone receptor, suggesting that @entity8290 -dependent endocytosis and sorting is also an important regulatory process in @entity1 cells. @entity1 receptors may also be down-regulated through the degradation of their cytosolic domains by a proteasome-dependent pathway.

XXXX -dependent internalization and down-regulation of plasma membrane proteins.

@entity1 :: ('9606', 'Species') :: ['mammalian', 'Mammalian'] @entity375 :: ('4932', 'Species') :: ['yeast', 'Saccharomyces cerevisiae'] @entity5537 :: ('MESH:D014498', 'Chemical') :: ['uracil'] @entity8290 :: ('850620(Tax:4932)', 'Gene') :: ['ubiquitin', 'Ubiquitin']
@entity8290 :: (850620(Tax:4932),Gene) :: ['Ubiquitin']
