Calpain 1 induce lysosomal permeabilization by cleavage of lysosomal associated membrane protein 2

Abstract

In light induced retinal degeneration (LIRD) photoreceptor cell death is mediated by caspase independent mechanisms. The activation of LEI/L-DNase II pathway in this model, is due to cathepsin D release from lysosomes, although the underlying mechanism remains poorly understood. In this paper we studied the involvement of calpains in lysosomal permeabilization. We investigated, for the first time, the calpain targets at lysosomal membrane level. We found that calpain 1 is responsible for lysosomal permeabilization by cleavage of the lysosomal associated membrane protein 2 (LAMP 2). Moreover, LAMP 2 degradation and lysosomal permeabilization were rescued by calpain inhibition and the use of MEF(-/-)lamp 2 cells indicates that the cleavage of LAMP 2A is essential for this permeabilization. Finally, we found that LAMP 2 is cleaved in LIRD, suggesting that the mechanism of calpain induced lysosomal permeabilization is not exclusive of a single cell death model. Overall, these data shed new light on understanding the mechanisms of lysosomal and caspase-independent cell death and point to the original targets for development of the new therapeutic protocols.

Retinal damage induced by commercial light emitting diodes (LEDs)

“…This is not surprising since this system is usually activated by metabolic stress [51]. It is also interesting to note that AIF and L-DNase II activation can be mediated by the activation of calpain 1, the first directly, by cleavage and release from the mitochondrial inner membrane [52][53], the second indirectly by permeabilizing lysosomes and releasing cathepsin D [54]. Moreover, although theses effectors have originally been described as mediating apoptosis, AIF has been shown to mediate necroptosis [55] and LEI/L-DNase II, due to its activation by lysosomal enzymes, could be also an effector of necrosis [56].…”

Lysosomal membrane permeabilization and autophagy blockade contribute to photoreceptor cell death in a mouse model of retinitis pigmentosa

“…48 Calpain cleavage of other essential lysosomal proteins, such as Lamp-2, has also been recently reported. 49 It is thus tempting to speculate that similar degradation of essential lysosomal proteins could participate in lysosomal damage in rd10 retinas.…”

On the use of an appropriate TdT-mediated dUTP–biotin nick end labeling assay to identify apoptotic cells

“…Different proteases can transform LEI into L-DNase II: intracellular elastases, AP-24 (apoptotic protease 24 kDa) [9] or other serine proteases [19]. Subsequently, L-DNase II can also be activated by cathepsin D as consequence of lysosomal membrane permeabilization [20]. LDNase II, like most acid endonucleases, generates 3'-P ends [21].…”