Annexins are a family of proteins that bind phospholipids in a calcium-dependent 
manner. Analysis of the sequences of the different members of the annexin family 
revealed the presence of a pentapeptide biochemically related to KFERQ in some 
annexins but not in others. Such sequences have been proposed to be a targeting 
sequence for chaperone-mediated autophagy, a lysosomal pathway of protein 
degradation that is activated in confluent cells in response to removal of serum 
growth factors. We demonstrate that annexins II and VI, which contain KFERQ-like 
sequences, are degraded more rapidly in response to serum withdrawal, while 
annexins V and XI, without such sequences, are degraded at the same rate in the 
presence and absence of serum. Using isolated lysosomes, only the annexins 
containing KFERQ-like sequences are degraded by chaperone mediated-autophagy. 
Annexins V and XI could associate with lysosomes but did not enter the lysosomes 
and were not proteolytic substrates. Furthermore, four annexins containing 
KFERQ-like sequences, annexins I, II, IV, and VI, are enriched in lysosomes with 
high chaperone-mediated autophagy activity as expected for substrate proteins. 
These results provide striking evidence for the importance of KFERQ motifs in 
substrates of chaperone-mediated autophagy.