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Updated: Apr 17, 2026
Identification of Kinase-substrate Pairs Using High Throughput Screening
Published on: August 29, 2015
Identification of rictor as a novel substrate of Polo-like kinase 1
1a Department of Biochemistry ; Purdue University ; West Lafayette , IN USA.
Abstract:
Plk1 has been essentially described as a critical regulator of many mitotic events. However, increasing evidence supports the notion that its molecular functions are not restricted to the cell cycle. In particular, recent reports suggest the existence of a molecular and functional link between Plk1 and the mammalian target of rapamycin (mTOR) pathway, which controls cell growth and proliferation via the raptor-mTOR (TORC1) and rictor-mTOR (TORC2) protein complexes. Herein, we have identified rapamycin-insensitive companion of mTOR (Rictor), a core component of mTORC2, as a new Plk1 substrate and have shown that Plk1 phosphorylates Rictor at Ser1162 in vitro and in vivo. Surprisingly, cells expressing the unphosphorylatable mutant (S1162A) of Rictor did not show any effect on well characterized canonical PI3K-mTOR pathway. However, we found that cells expressing the unphosphorylatable form of Rictor have an elevated level of mSin1 isoform (mSin1.5). Considering that mSin1.5-containing mTORC2 was reported to associate with stress signaling, we propose that phosphorylation of Rictor at Ser1162 by Plk1 might be involved in a novel signaling pathway by regulating the mSin1.5-defined mTORC2.
Insights
Polo-like kinase 1 (Plk1) phosphorylates Rictor, a key mTORC2 component, at Ser1162. This phosphorylation regulates the mSin1.5 isoform, potentially revealing a new Plk1-mTORC2 signaling pathway beyond cell cycle control.
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Polo-like kinase 1 (Plk1) is a critical regulator of mitosis.
- Emerging evidence suggests Plk1's functions extend beyond the cell cycle.
- The mammalian target of rapamycin (mTOR) pathway controls cell growth and proliferation.
Purpose of the Study:
- To investigate the potential link between Plk1 and the mTOR pathway.
- To identify new substrates of Plk1 involved in cellular signaling.
- To elucidate the role of Rictor phosphorylation by Plk1.
Main Methods:
- In vitro and in vivo phosphorylation assays.
- Site-directed mutagenesis to create unphosphorylatable Rictor mutants (S1162A).
- Analysis of mTOR pathway components and isoforms.
Main Results:
- Rictor, a component of mTORC2, was identified as a novel Plk1 substrate.
- Plk1 phosphorylates Rictor at Ser1162.
- The S1162A Rictor mutant did not affect canonical PI3K-mTOR signaling but led to elevated mSin1.5 levels.
- Elevated mSin1.5 suggests a role in stress signaling.
Conclusions:
- Plk1 directly phosphorylates Rictor at Ser1162.
- This phosphorylation event may regulate a novel mTORC2-mediated signaling pathway involving mSin1.5.
- Plk1's role may extend to stress response pathways via mTORC2 regulation.
