Year-end Sale % OFF 
Abstract
Phosphatidylinositides play important roles in cellular signaling and migration. Phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) is an important phosphatidylinositide because it acts as a secondary messenger to trigger cell movement and proliferation. A high level of PI(3,4,5)P3 at the plasma membrane is known to contribute to tumorigenesis. One key enzyme that regulates PI(3,4,5)P3 levels at the plasma membrane is phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which dephosphorylates PI(3,4,5)P3 through hydrolysis to form phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). It has been reported that PI(4,5)P2 is involved in positive feedback in the PI(3,4,5)P3 hydrolysis by PTEN. However, how PI(3,4,5)P3 dephosphorylation by PTEN is regulated, is still under debate. How other PI(3,4,5)P3-binding proteins affect the dephosphorylation kinetics catalyzed by PTEN also remains unclear. Here, we develop a fluorescent-protein biosensor approach to study how PI(3,4,5)P3 dephosphorylation is regulated by PTEN as well as its membrane-mediated feedback mechanisms. Our observation of sigmoidal kinetics of the PI(3,4,5)P3 hydrolysis reaction supports the notion of autocatalysis in PTEN function. We developed a kinetic model to describe the observed reaction kinetics, which allowed us to i) distinguish between membrane-recruitment and allosteric activation of PTEN by PI(4,5)P2, ii) account for the influence of the biosensor on the observed reaction kinetics, and iii) demonstrate that all of these mechanisms contribute to the kinetics of PTEN-mediated catalysis.
Highlights
The phosphatase PTEN regulates the well-known phosphoinositide 3-OH kinases (PI3K) / AKT pathway that is central in many cellular processes including cell growth, differentiation, and apoptosis [1]
To study the biosensor / membrane interaction, the PI(3,4,5)P3 sensor YFP-PHGrp1 was injected into the measurement chamber, and its signal change on the membrane surface was monitored through total internal reflection fluorescence microscopy (TIRF) imaging
At a flow velocity of 1 cm/s, we found a dead time of about 2 s, which is substantially shorter than the time frame over which relevant membrane mediated kinetics occurred
Summary
The phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10) regulates the well-known PI3K / AKT pathway that is central in many cellular processes including cell growth, differentiation, and apoptosis [1]. PTEN hydrolyses the phosphatidylinositol3,4,5-trisphosphate PI(3,4,5)P3 at the 3-OH position of the inositol ring. This process downregulates membrane binding and subsequent activation of the serine-threonine protein kinase AKT ( called protein kinase B), which has many cellular downstream effectors. Up-regulation of this pathway occurs through phosphoinositide 3-OH kinases (PI3K).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
