DECREASED PROTEIN DEGRADATION IN AGING

DESCRIPTION (provided by applicant): Rates of protein degradation decrease with age contributing to abnormal accumulation of proteins in tissues and possible loss of function. We have previously found that the activity of chaperone mediated autophagy (CMA), a selective mechanism for the degradation of cytosolic proteins in lysosomes, declines with age. CMA is preferentially activated during stress and can account for as much as 30% of total protein degradation. Reduced CMA with age could contribute to the accumulation of abnormal proteins in the cytosol of senescent cells, as well as to the impaired ability of these cells to adapt to stress conditions. The limiting step for CMA is the binding of substrate proteins to a receptor at the lysosomal membrane, the lysosome membrane associated protein type 2a (lamp2a). We have found that levels of this receptor are reduced in lysosomes from old rodents and senescent cells. We now propose to elucidate the physiological consequences of the age-related reduction of CMA and to determine whether restoration of CMA activity can revert these abnormalities. We intend to answer the following questions: Why do the receptor levels decrease with age? What are the consequences of reduced CMA? Is it possible to correct impaired CMA by augmenting levels of the receptor in old animals? To address these questions we will: 1) Determine how the levels of the receptor are regulated under different cellular conditions; 2) Inhibit CMA in cultured cells and analyze the cellular consequences; 3) Characterize the changes with age in CMA in a transgenic mouse generated in our laboratory in which the levels of lamp2a can be regulated. If we successfully restore CMA in the old members of this mouse colony we will analyze possible beneficial effects in accumulated aberrant proteins and in the response to stress of these animals. If only a partial restoration is attained, we will combine in the future similar restorative attempts for any other defective component(s) identified through this project.