Related Experiment Video

Updated: Jul 3, 2026

Purification of Ubiquitinated p53 Proteins from Mammalian Cells
10:55

Purification of Ubiquitinated p53 Proteins from Mammalian Cells

Published on: March 21, 2022

A new ubiquitin ligase involved in p57KIP2 proteolysis regulates osteoblast cell differentiation

Minsoo Kim1, Takashi Nakamoto, Shigeki Nishimori

  • 1Laboratory of Frontier Science, Core Technology and Research Center, Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.

EMBO Reports
|July 29, 2008
PubMed

Insights

Transforming growth factor-beta1 (TGF-beta1) triggers osteoblast differentiation inhibition by degrading p57(KIP2). F-box protein 12 (FBL12) mediates this degradation, revealing a new regulatory mechanism for osteoblast development.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Developmental Biology

Background:

  • Transforming growth factor-beta1 (TGF-beta1) is a key regulator of numerous physiological processes, including the inhibition of osteoblast differentiation.
  • Previous studies indicated that TGF-beta1 stimulation leads to the degradation of p57(KIP2) in osteoblasts, a process linked to the ubiquitin-proteasome pathway and SMAD-mediated transcription.
  • The precise molecular mechanisms governing p57(KIP2) degradation in response to TGF-beta1 remained largely unelucidated.

Purpose of the Study:

  • To identify the molecular players involved in TGF-beta1-induced p57(KIP2) degradation in osteoblasts.
  • To elucidate the role of F-box protein 12 (FBL12) in the regulation of p57(KIP2) stability and osteoblast differentiation.

Main Methods:

  • Investigated the interaction between FBL12 and p57(KIP2) using techniques such as RNA interference and dominant-negative mutants.
  • Assessed the ubiquitination of p57(KIP2) mediated by the SCF(FBL12) complex.
  • Examined the effects of FBL12 manipulation on p57(KIP2) levels and primary osteoblast differentiation.

Main Results:

  • Identified F-box protein 12 (FBL12) as a novel protein involved in TGF-beta1-induced p57(KIP2) degradation.
  • Demonstrated that FBL12 forms an SCF(FBL12) complex and directly ubiquitinates p57(KIP2) in a phosphorylation-dependent manner.
  • Showed that inhibiting FBL12 suppresses p57(KIP2) degradation, while a dominant-negative FBL12 mutant increases p57(KIP2) levels.
  • Observed that wild-type FBL12 inhibits osteoblast differentiation, whereas FBL12DeltaF promotes it, correlating with p57(KIP2) levels.

Conclusions:

  • FBL12 plays a critical role in the TGF-beta1-induced degradation of p57(KIP2) in osteoblasts.
  • The FBL12-mediated degradation of p57(KIP2) is a key regulatory mechanism controlling osteoblast differentiation.
  • These findings uncover a novel pathway influencing bone cell development and provide potential targets for therapeutic interventions.

More Related Videos

Detection of Protein Ubiquitination09:00

Detection of Protein Ubiquitination

Published on: August 19, 2009

Evaluation of Substrate Ubiquitylation by E3 Ubiquitin-ligase in Mammalian Cell Lysates09:47

Evaluation of Substrate Ubiquitylation by E3 Ubiquitin-ligase in Mammalian Cell Lysates

Published on: May 10, 2022

Related Concept Videos

Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
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.
The Proteasome01:13

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...
The Proteasome02:18

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
Abnormal Proliferation02:23

Abnormal Proliferation

Under normal conditions, most adult cells remain in a non-proliferative state unless stimulated by internal or external factors to replace lost cells. Abnormal cell proliferation is a condition in which the cell's growth exceeds and is uncoordinated with normal cells. In such situations, cell division persists in the same excessive manner even after cessation of the stimuli, leading to persistent tumors. The tumor arises from the damaged cells that replicate to pass the damage to the daughter...