The selective degradation of cytosolic proteins in lysosomes by 
chaperone-mediated autophagy depends, at least in part, on the levels of a 
substrate receptor at the lysosomal membrane. We have previously identified this 
receptor as the lysosome-associated membrane protein type 2a (lamp2a) and showed 
that levels of lamp2a at the lysosomal membrane directly correlate with the 
activity of the proteolytic pathway. Here we show that levels of lamp2a at the 
lysosomal membrane are mainly controlled by changes in its half-life and its 
distribution between the lysosomal membrane and the matrix. The lysosomal 
degradation of lamp2a requires the combined action of at least two different 
proteolytic activities at the lysosomal membrane. Lamp2a is released from the 
membrane by the action of these proteases, and then the truncated lamp2a is 
rapidly degraded within the lysosomal matrix. Membrane degradation of lamp2a is 
a regulated process that is inhibited in the presence of substrates for 
chaperone-mediated autophagy and under conditions that activate that type of 
autophagy. Uptake of substrate proteins also results in transport of some intact 
lamp2a from the lysosomal membrane into the matrix. This fraction of lamp2a can 
be reinserted back into the lysosomal membrane. The traffic of lamp2a through 
the lysosomal matrix is not mediated by vesicles, and lamp2a reinsertion 
requires the lysosomal membrane potential and protein components of the 
lysosomal membrane. The distribution of lamp2a between the lysosomal membrane 
and matrix is a dynamic process that contributes to the regulation of lysosomal 
membrane levels of lamp2a and consequently to the activity of the 
chaperone-mediated autophagic pathway.