Functional definition of relevant epitopes on the tumor suppressor PTEN protein.
The binding of PTEN to PDZ-domain-containing proteins appears to play an important role in the control of cell growth, motility and apoptosis. In turn, this binding can be abrogated by cleavage of the PTEN C-terminal region by caspase-3. We have generated and characterized monoclonal antibodies (mAb) directed against distinct epitopes at the C-terminal region of PTEN, and used them to define protein-binding epitopes on PTEN and to study its cleavage by caspase-3. mAb directed against epitopes at the far C-terminus of PTEN blocked binding to PTEN cognate PDZ domains and did not recognize the caspase-3 cleaved PTEN fragments. On the other hand, mAb that recognized an epitope within the C2 domain of PTEN did not prevent binding to PDZ domains, but could detect the caspase-3 cleaved PTEN fragments. The analysis of PTEN cleavage by caspase-3 revealed that the lipid phosphatase activity of PTEN controls its own degradation by interfering with the PI3-K anti-apoptotic activity. Our results define protein-binding sites on the PTEN tumor suppressor at the immunochemical level, and suggest a regulatory link between PTEN phosphatase activity, caspase-3 sensitivity and PTEN-protein interactions.
Andrés-Pons
Amparo
A
Instituto de Investigaciones Citológicas/FVIB, Amadeo de Saboya 4, Valencia 46010, Spain.
Valiente
Miguel
M
Torres
Josema
J
Gil
Anabel
A
Roglá
Isabel
I
Ripoll
Francisca
F
Cervera
Javier
J
Pulido
Rafael
R
D001665:Binding Sites; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D000939:Epitopes; D016147:Genes, Tumor Suppressor; D006801:Humans; D007150:Immunohistochemistry; D009363:Neoplasm Proteins; D009369:Neoplasms / Q000503:physiopathology; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000502:physiology*
D000939:Epitopes; D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases