Related Experiment Video

Updated: Jul 5, 2026

Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death
09:18

Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death

Published on: December 27, 2016

Multisite phosphorylation regulates Bim stability and apoptotic activity

Anette Hübner1, Tamera Barrett, Richard A Flavell

  • 1Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA.

Molecular Cell
|May 24, 2008
PubMed

Insights

Investigating Bim protein phosphorylation in mice revealed that altering specific sites impacts cell death regulation. Phosphorylation changes affect Bim binding to Bcl2 and its degradation, influencing cell survival and apoptosis sensitivity.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The BH3-only protein Bim is a key regulator of apoptosis (programmed cell death).
  • Multisite phosphorylation of Bim by MAP kinases is a known regulatory mechanism controlling its apoptotic function.
  • Understanding Bim phosphorylation's in vivo role is crucial for deciphering cell death signaling pathways.

Purpose of the Study:

  • To investigate the in vivo functional consequences of Bim phosphorylation.
  • To elucidate how specific phosphorylation sites on Bim modulate its interaction with Bcl2 and its degradation.
  • To determine the contribution of differential Bim phosphorylation to cellular apoptotic responses.

Main Methods:

  • Generation of mice expressing phosphorylation-defective Bim mutant proteins.
  • Analysis of Bim binding affinity to the antiapoptotic protein Bcl2.
  • Assessment of Bim protein stability and proteasomal degradation rates.
  • Evaluation of cellular apoptosis sensitivity in response to Bim mutations.

Main Results:

  • Mutation of the Thr-112 phosphorylation site reduced Bim binding to Bcl2, leading to increased cell survival.
  • Mutations at Ser-55, Ser-65, and Ser-73 sites resulted in increased apoptosis due to impaired proteasomal degradation of Bim.
  • These findings demonstrate distinct roles for different Bim phosphorylation sites.

Conclusions:

  • Bim phosphorylation regulates its apoptotic activity through multiple mechanisms.
  • Phosphorylation of different Bim sites differentially impacts its interaction with Bcl2 and its degradation.
  • These phosphorylation-dependent regulatory events are critical determinants of cellular sensitivity to apoptosis.

More Related Videos

Exploring Caspase Mutations and Post-Translational Modification by Molecular Modeling Approaches05:56

Exploring Caspase Mutations and Post-Translational Modification by Molecular Modeling Approaches

Published on: October 13, 2022

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay12:26

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

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...
Covalently Linked Protein Regulators02:04

Covalently Linked Protein Regulators

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein.
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Phosphorylation01:02

Phosphorylation

The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Interactions Between Signaling Pathways01:19

Interactions Between Signaling Pathways

Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
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...