Related Experiment Videos

Enhanced phosphatidylinositol 3-kinase activity and high phosphorylation state of its downstream signalling molecules

H Murakami1, T Iwashita, N Asai

  • 1Department of Pathology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan.

Biochemical and Biophysical Research Communications
|August 17, 1999
PubMed

Insights

Glial cell line-derived neurotrophic factor (GDNF) and mutations in multiple endocrine neoplasia (MEN) 2B activate intracellular signaling pathways more strongly than MEN 2A. This suggests higher PI 3-kinase activation may link to MEN 2B clinical features.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Oncology

Background:

  • The Ret tyrosine kinase pathway is crucial in cellular signaling and is implicated in various cancers.
  • Multiple Endocrine Neoplasia (MEN) types 2A and 2B are genetic disorders associated with Ret mutations, presenting distinct clinical phenotypes.

Purpose of the Study:

  • To compare intracellular signaling pathway activation by glial cell line-derived neurotrophic factor (GDNF) and distinct Multiple Endocrine Neoplasia (MEN) mutations (2A vs. 2B).
  • To elucidate the role of phosphatidylinositol 3-kinase (PI 3-kinase) and its downstream effectors in the differential signaling observed.

Main Methods:

  • Investigated Ret tyrosine kinase signaling pathways.
  • Utilized cell transfection models expressing MEN 2A or MEN 2B mutations.
  • Measured tyrosine phosphorylation of key signaling proteins including Gab1, p62Dok, and PKB/Akt.
  • Assessed the activation of PI 3-kinase and its interactions with downstream molecules.

Main Results:

  • GDNF stimulation and MEN 2B mutations induced higher levels of Gab1 tyrosine phosphorylation and PI 3-kinase activation compared to MEN 2A mutations.
  • Phosphorylated Gab1 was identified as a key interactor with active PI 3-kinase.
  • PKB/Akt and p62Dok phosphorylation occurred in a PI 3-kinase-dependent manner, with significantly higher levels in MEN 2B transfectants.
  • MEN 2B-associated p62Dok phosphorylation led to complex formation with RasGAP and Nck.

Conclusions:

  • The study demonstrates differential activation of intracellular signaling pathways by GDNF and MEN mutations.
  • Higher activation of PI 3-kinase and its downstream signaling molecules in MEN 2B is associated with the observed clinical phenotype.
  • These findings provide insights into the molecular mechanisms underlying MEN 2B pathogenesis.

Related Concept Videos

PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

The mammalian target of rapamycin or mTOR protein was discovered in 1994 due to its direct interaction with rapamycin. The protein gets its name from a yeast homolog called TOR. The mTOR protein complex in mammalian cells plays a major role in balancing anabolic processes such as the synthesis of proteins, lipids, and nucleotides and catabolic processes, such as autophagy in response to environmental cues, such as availability of nutrients and growth factors.
The mTOR pathway or the...
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
Receptor Tyrosine Kinases01:26

Receptor Tyrosine Kinases

Receptor tyrosine kinases or RTKs are membrane-bound receptors that phosphorylate specific tyrosine on protein substrates. RTKs regulate cellular growth, differentiation, survival, and migration. They contain an extracellular ligand binding domain, a transmembrane domain, and a cytosolic tail with intrinsic kinase activity. Several extracellular signaling molecules activate RTKs in one or more ways and relay the signal downstream. Ligands such as platelet-derived growth factor (PDGF) or...