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Updated: Aug 29, 2026

A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl
05:20

A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl

Published on: November 28, 2014

The granzyme B-serglycin complex from cytotoxic granules requires dynamin for endocytosis

Kirstin Veugelers1, Bruce Motyka, Christine Frantz

  • 1Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.

Blood
|January 24, 2004
PubMed

Insights

Cytotoxic T lymphocytes use dynamin-dependent pathways to deliver granzymes into target cells. This mechanism is crucial for immune cell-mediated killing and granzyme uptake.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells eliminate target cells through directed exocytosis of cytotoxic molecules like perforin and granzymes.
  • The precise mechanism of granzyme entry into target cells remains debated, with ongoing discussion about non-specific endocytosis versus pathways involving the cation-independent mannose 6-phosphate receptor.

Purpose of the Study:

  • To investigate the role of dynamin, a key endocytic protein, in the uptake and cytotoxic activity of granzyme B.
  • To determine whether granzyme B entry into target cells is dynamin-dependent or -independent.

Main Methods:

  • Testing the uptake and killing activity of purified granzyme B.
  • Analyzing the effect of dynamin pathway defects on killing by live CTLs.
  • Investigating the uptake of serglycin-bound granzyme B from CTL degranulate material.

Main Results:

  • Purified granzyme B uptake and killing occurred via both dynamin-dependent and -independent pathways.
  • Serglycin-bound granzyme B within CTL degranulate material primarily utilized a dynamin-dependent pathway for target cell killing.
  • Impaired dynamin endocytic pathways attenuated killing by live CTLs, specifically affecting granzyme B-associated pathways.

Conclusions:

  • Degranulated, serglycin-bound granzymes necessitate dynamin for efficient uptake into target cells.
  • Dynamin plays a significant role in the cytotoxic mechanism of CTLs and NK cells.
  • The findings support a model where dynamin-mediated endocytosis is critical for granzyme-mediated cytotoxicity.

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