PTEN is recruited to specific microdomains of the plasma membrane during lactacystin-induced neuronal apoptosis.
The tumor suppressor PTEN (phosphatase and tensin homolog deleted from chromosome 10) is a novel phosphatase displaying both protein and lipid phosphatase activities. In the central nervous system, PTEN plays an important role in the regulation of cell growth, differentiation and death. The tumor suppressor function of PTEN is attributed to its phospholipid phosphatase activity that dephosphorylates the plasma membrane phosphatidylinositol-(3,4,5)-triphosphate (PtdIns(3,4,5)P(3)). Since PTEN is normally localized in the cytosol, it needs to be targeted to the plasma membrane to dephosphorylate PtdIns(3,4,5)P(3). We previously demonstrated that lactacystin-induced apoptosis of culture cortical neuron is associated with: (i) cleavage of PTEN (55 kDa) to a 50 kDa truncated form and (ii) accumulation of PTEN and all the truncated PTEN in a detergent-insoluble membrane fraction of the neuronal cells. Herein we demonstrate that a caspase-3 inhibitor suppresses cleavage of PTEN to the 50kDa truncated form in culture cortical neurons in response to lactacystin treatment. Using immunogold transmission electron microscopy, we examined the distribution of PTEN in plasma membrane sheets stripped from cultured cortical neurons with and without treatment of lactacystin. Our results demonstrate that lactacystin treatment induces accumulation of PTEN to the inner surface of the plasma membrane sheets of the neuronal cells. Taken together, our data suggest that caspase-3-like proteases are involved in the conversion of PTEN to a 50-kDa truncated form and that PTEN and its truncated form accumulate at specific microdomains of the plasma membrane in neuronal cells undergoing apoptosis.
Choy
Meng Shyan
MS
Departments of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Blk MD7, 8 Medical Drive, Singapore 117597, Singapore.
Bay
Boon Huat
BH
Cheng
Heung-Chin
HC
Cheung
Nam Sang
NS
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D061988:Proteasome Inhibitors; D021381:Protein Transport
D061988:Proteasome Inhibitors; C067713:lactacystin; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse; D000111:Acetylcysteine