Endocytic down-regulation of ErbB2 is stimulated by cleavage of its C-terminus.

TY - JOUR

T1 - Endocytic down-regulation of ErbB2 is stimulated by cleavage of its C-terminus.

AU - Lerdrup, Mads

AU - Bruun, Silas

AU - Grandal, Michael Vibo

AU - Roepstorff, Kirstine

AU - Kristensen, Malene M

AU - Hommelgaard, Anette M

AU - van Deurs, Bo

N1 - Keywords: Benzoquinones; Cell Membrane; Down-Regulation; Endocytosis; Humans; Lactams, Macrocyclic; Lysosomes; Mutant Proteins; Proteasome Endopeptidase Complex; Receptor, erbB-2; Recombinant Fusion Proteins; Reproducibility of Results; Structure-Activity Relationship

PY - 2007

Y1 - 2007

N2 - High ErbB2 levels are associated with cancer, and impaired endocytosis of ErbB2 could contribute to its overexpression. Therefore, knowledge about the mechanisms underlying endocytic down-regulation of ErbB2 is warranted. The C-terminus of ErbB2 can be cleaved after various stimuli, and after inhibition of HSP90 with geldanamycin this cleavage is accompanied by proteasome-dependent endocytosis of ErbB2. However, it is unknown whether C-terminal cleavage is linked to endocytosis. To study ErbB2 cleavage and endocytic trafficking, we fused yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP) to the N- and C-terminus of ErbB2, respectively (YFP-ErbB2-CFP). After geldanamycin stimulation YFP-ErbB2-CFP became cleaved in nonapoptotic cells in a proteasome-dependent manner, and a markedly larger relative amount of cleaved YFP-ErbB2-CFP was observed in early endosomes than in the plasma membrane. Furthermore, cleavage took place at the plasma membrane, and cleaved ErbB2 was internalized and degraded far more efficiently than full-length ErbB2. Concordantly, a C-terminally truncated ErbB2 was also readily endocytosed and degraded in lysosomes compared with full-length ErbB2. Altogether, we suggest that geldanamycin leads to C-terminal cleavage of ErbB2, which releases the receptor from a retention mechanism and causes endocytosis and lysosomal degradation of ErbB2.

AB - High ErbB2 levels are associated with cancer, and impaired endocytosis of ErbB2 could contribute to its overexpression. Therefore, knowledge about the mechanisms underlying endocytic down-regulation of ErbB2 is warranted. The C-terminus of ErbB2 can be cleaved after various stimuli, and after inhibition of HSP90 with geldanamycin this cleavage is accompanied by proteasome-dependent endocytosis of ErbB2. However, it is unknown whether C-terminal cleavage is linked to endocytosis. To study ErbB2 cleavage and endocytic trafficking, we fused yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP) to the N- and C-terminus of ErbB2, respectively (YFP-ErbB2-CFP). After geldanamycin stimulation YFP-ErbB2-CFP became cleaved in nonapoptotic cells in a proteasome-dependent manner, and a markedly larger relative amount of cleaved YFP-ErbB2-CFP was observed in early endosomes than in the plasma membrane. Furthermore, cleavage took place at the plasma membrane, and cleaved ErbB2 was internalized and degraded far more efficiently than full-length ErbB2. Concordantly, a C-terminally truncated ErbB2 was also readily endocytosed and degraded in lysosomes compared with full-length ErbB2. Altogether, we suggest that geldanamycin leads to C-terminal cleavage of ErbB2, which releases the receptor from a retention mechanism and causes endocytosis and lysosomal degradation of ErbB2.

U2 - 10.1091/mbc.E07-01-0025

DO - 10.1091/mbc.E07-01-0025

M3 - Journal article

C2 - 17626164

SN - 1059-1524

VL - 18

SP - 3656

EP - 3666

JO - Molecular Biology of the Cell

JF - Molecular Biology of the Cell

IS - 9

ER -