Cell structure
9
1
RETPaHC
may also be secreted – often as part of a process to alter the extracellular A
matrix, as in osteoclast-mediated erosion during bone resorption. For
further reading on lysosome biogenesis, see Saftig and Klumperman
(2009).
lysosomal dysfunction
Lysosomal storage diseases (LSDs) are a consequence of lysosomal
dysfunction. Approximately 60 different types of LSD have been identi-
fied on the basis of the type of material accumulated in cells (such as
mucopolysaccharides, sphingolipids, glycoproteins, glycogen and lipo-
fuscins). LSDs are characterized by severe neurodegeneration, mental
decline, and cognitive and behavioural abnormalities. Autophagy
impairment caused by defective lysosome–autophagosome coupling
triggers a pathogenic cascade by the accumulation of substrates that
contribute to neurodegenerative disorders including Parkinson’s dis-
ease, Alzheimer’s disease, Huntington’s disease and several tau-opathies.
Many lysosomal storage diseases are known, e.g. Tay–Sachs disease