Myristoylated alanine-rich C-kinase substrate effector domain phosphorylation regulates the growth and radiation sensitization of glioblastoma

Int J Oncol. 2019 Jun;54(6):2039-2053. doi: 10.3892/ijo.2019.4766. Epub 2019 Mar 29.


Glioblastoma harbors frequent alterations in receptor tyrosine kinases, phosphatidylinositol‑3 kinase (PI3K) and phosphatase and tensin homolog (PTEN) that dysregulate phospholipid signaling driven tumor proliferation and therapeutic resistance. Myristoylated alanine‑rich C‑kinase substrate (MARCKS) is a 32 kDa intrinsically unstructured protein containing a polybasic (+13) effector domain (ED), which regulates its electrostatic sequestration of phospholipid phosphatidylinositol (4,5)‑bisphosphate (PIP2), and its binding to phosphatidylserine, calcium/calmodulin, filamentous actin, while also serving as a nuclear localization sequence. MARCKS ED is phosphorylated by protein kinase C (PKC) and Rho‑associated protein kinase (ROCK) kinases; however, the impact of MARCKS on glioblastoma growth and radiation sensitivity remains undetermined. In the present study, using a tetracycline‑inducible system in PTEN‑null U87 cells, we demonstrate that MARCKS overexpression suppresses growth and enhances radiation sensitivity in vivo. A new image cytometer, Xcyto10, was utilized to quantify differences in MARCKS ED phosphorylation on localization and its association with filamentous actin. The overexpression of the non‑phosphorylatable ED mutant exerted growth‑suppressive and radiation‑sensitizing effects, while the pseudo‑phosphorylated ED mutant exhibited an enhanced colony formation and clonogenic survival ability. The identification of MARCKS protein‑protein interactions using co‑immunoprecipitation coupled with tandem mass spectrometry revealed novel MARCKS‑associated proteins, including importin‑β and ku70. On the whole, the findings of this study suggest that the determination of the MARCKS ED phosphorylation status is essential to understanding the impact of MARCKS on cancer progression.

MeSH terms

  • Animals
  • Brain Neoplasms / mortality
  • Brain Neoplasms / pathology*
  • Brain Neoplasms / radiotherapy
  • Cell Line, Tumor
  • Cell Proliferation
  • Disease Progression
  • Female
  • Glioblastoma / mortality
  • Glioblastoma / pathology*
  • Glioblastoma / radiotherapy
  • Humans
  • Ku Autoantigen / metabolism
  • Mice
  • Mice, Nude
  • Myristoylated Alanine-Rich C Kinase Substrate / metabolism*
  • Phosphorylation
  • Protein Domains*
  • Protein Interaction Mapping
  • Radiation Tolerance*
  • Survival Analysis
  • Treatment Outcome
  • Xenograft Model Antitumor Assays
  • beta Karyopherins / metabolism


  • MARCKS protein, human
  • TNPO1 protein, human
  • beta Karyopherins
  • Myristoylated Alanine-Rich C Kinase Substrate
  • Xrcc6 protein, human
  • Ku Autoantigen