Vinculin controls PTEN protein level by maintaining the interaction of the adherens junction protein beta-catenin with the scaffolding protein MAGI-2.
PTEN is a frequently mutated tumor suppressor in malignancies. Interestingly, some malignancies exhibit undetectable PTEN protein without mutations or loss of PTEN mRNA. The cause(s) for this reduction in PTEN is unknown. Cancer cells frequently exhibit loss of cadherin, beta-catenin, alpha-catenin and/or vinculin, key elements of adherens junctions. Here we show that F9 vinculin-null (vin(-/-)) cells lack PTEN protein despite normal PTEN mRNA levels. Their PTEN protein expression was restored by transfection with vinculin or by inhibition of PTEN degradation. F9 vin(-/-) cells express PTEN protein upon transfection with a vinculin fragment (amino acids 243-1066) that is capable of interacting with alpha-catenin but unable to target into focal adhesions. On the other hand, disruption of adherens junctions with an E-cadherin blocking antibody reduced PTEN protein to undetectable levels in wild-type F9 cells. PTEN protein levels were restored in F9 vin(-/-) cells upon transfection with an E-cadherin-alpha-catenin fusion protein, which targets into adherens junctions and interacts with beta-catenin in F9 vin(-/-) cells. beta-Catenin is known to interact with MAGI-2. MAGI-2 interaction with PTEN in the cell membrane is known to prevent PTEN protein degradation. Thus, MAGI-2 overexpression in F9 vin(-/-) cells restored PTEN protein levels. Moreover, expression of vinculin mutants that reinstated the disrupted interactions of beta-catenin with MAGI-2 in F9 vin(-/-) cells also restored PTEN protein levels. These studies indicate that PTEN protein levels are dependent on the maintenance of beta-catenin-MAGI-2 interaction, in which vinculin plays a critical role.
Subauste
M Cecilia
MC
Department of Cell Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA. mcssub@scripps.edu
Nalbant
Perihan
P
Adamson
Eileen D
ED
Hahn
Klaus M
KM
D022005:Adherens Junctions / Q000502:physiology*; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation / Q000235:genetics; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D016596:Vinculin / Q000235:genetics / Q000378:metabolism*; D051178:alpha Catenin; D051176:beta Catenin
C495267:CTNNB1 protein, mouse; D015820:Cadherins; C495272:Ctnna1 protein, mouse; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D051178:alpha Catenin; D051176:beta Catenin; D016596:Vinculin; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; D046988:Proteasome Endopeptidase Complex