Related Experiment Video

Updated: Jul 7, 2026

An Adoptive Transfer Model of Rheumatoid Arthritis in Mice
07:37

An Adoptive Transfer Model of Rheumatoid Arthritis in Mice

Published on: June 6, 2025

Cathepsin K-dependent toll-like receptor 9 signaling revealed in experimental arthritis

Masataka Asagiri1, Toshitake Hirai, Toshihiro Kunigami

  • 1Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, Tokyo 113-8549, Japan.

Science (New York, N.Y.)
|February 2, 2008
PubMed

Insights

Inhibiting cathepsin K suppresses autoimmune diseases by reducing joint inflammation and bone resorption. This protease also impacts immune cell signaling, suggesting it as a therapeutic target for autoimmune conditions.

Area of Science:

  • Immunology
  • Rheumatology
  • Molecular Biology

Background:

  • Cathepsin K is a lysosomal protease primarily known for its role in osteoclast function.
  • Inhibitors of cathepsin K have been explored for potential therapeutic applications.

Purpose of the Study:

  • To investigate the role of cathepsin K in autoimmune diseases.
  • To evaluate cathepsin K as a potential therapeutic target for autoimmune conditions.

Main Methods:

  • Utilized cathepsin K knockout (cathepsin K-/-) mice and pharmacological inhibitors.
  • Assessed the effects of cathepsin K inhibition on autoimmune arthritis and experimental autoimmune encephalomyelitis.
  • Analyzed Toll-like receptor 9 signaling in dendritic cells and T helper 17 cell induction.

Main Results:

  • Cathepsin K inhibition effectively suppressed joint inflammation and osteoclast bone resorption in autoimmune arthritis.
  • Cathepsin K-/- mice exhibited resistance to experimental autoimmune encephalomyelitis.
  • Pharmacological inhibition or genetic disruption of cathepsin K impaired Toll-like receptor 9 signaling in dendritic cells, leading to reduced T helper 17 cell induction without affecting antigen presentation.

Conclusions:

  • Cathepsin K plays a significant role in the immune system, particularly in the pathogenesis of autoimmune diseases.
  • Targeting cathepsin K presents a promising therapeutic strategy for managing autoimmune inflammatory conditions.

Related Concept Videos

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...
T Cell Types and Functions01:24

T Cell Types and Functions

When T cells with CD4 markers are activated, they give rise to two types of effector cells: helper T cells and regulatory T cells. Meanwhile, T cells with CD8 markers differentiate into effector cytotoxic T cells. The differentiation of CD4 T cells into helper T cell subsets, such as Th1, Th2, and Th17 cells, is dependent on the antigen type, antigen-presenting cell, and regulatory cytokines.
Th1 cells stimulate dendritic cells to express necessary co-stimulatory molecules on their surfaces for...
NF-κB-dependent Signaling Pathway02:26

NF-κB-dependent Signaling Pathway

The transcription factor NF-κB was discovered in 1986 in the lab of Nobel laureate Professor David Baltimore, for its interaction with the immunoglobulin light chain enhancer in B-cells. After more than three decades of study, it is now evident that NF-κB regulates the expression of over 100 genes. Most of these genes play an essential role in the innate and adaptive immune responses as well as the inflammatory responses of animals.
NF-κB-dependent Signaling Mechanism
The heterodimer of NF-κB...