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Updated: Jun 17, 2025
Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism
Published on: December 18, 2013
Distinct conformational states enable transglutaminase 2 to promote cancer cell survival versus cell death
Cody Aplin1,2, Kara A Zielinski3, Suzette Pabit3
1Department of Chemistry and Chemical Biology, Cornell University, 14853, Ithaca, NY, USA.
Abstract:
Transglutaminase 2 (TG2) is a GTP-binding, protein-crosslinking enzyme that has been investigated as a therapeutic target for Celiac disease, neurological disorders, and aggressive cancers. TG2 has been suggested to adopt two conformational states that regulate its functions: a GTP-bound, closed conformation, and a calcium-bound, crosslinking-active open conformation. TG2 mutants that constitutively adopt an open conformation are cytotoxic to cancer cells. Thus, small molecules that bind and stabilize the open conformation of TG2 could offer a new therapeutic strategy. Here, we investigate TG2, using static and time-resolved small-angle X-ray scattering (SAXS) and single-particle cryoelectron microscopy (cryo-EM), to determine the conformational states responsible for conferring its biological effects. We also describe a newly developed TG2 inhibitor, LM11, that potently kills glioblastoma cells and use SAXS to investigate how LM11 affects the conformational states of TG2. Using SAXS and cryo-EM, we show that guanine nucleotides bind and stabilize a monomeric closed conformation while calcium binds to an open state that can form higher order oligomers. SAXS analysis suggests how a TG2 mutant that constitutively adopts the open state binds nucleotides through an alternative mechanism to wildtype TG2. Furthermore, we use time resolved SAXS to show that LM11 increases the ability of calcium to bind and stabilize an open conformation, which is not reversible by guanine nucleotides and is cytotoxic to cancer cells. Taken together, our findings demonstrate that the conformational dynamics of TG2 are more complex than previously suggested and highlight how conformational stabilization of TG2 by LM11 maintains TG2 in a cytotoxic conformational state.
Insights
Transglutaminase 2 (TG2) enzyme dynamics were explored. A new inhibitor, LM11, stabilizes a cytotoxic open conformation of TG2, offering a potential cancer therapy strategy.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Transglutaminase 2 (TG2) is a key enzyme in cellular processes, implicated in diseases like Celiac disease, neurological disorders, and cancer.
- TG2 exists in distinct conformational states (closed/GTP-bound and open/calcium-bound) that regulate its enzymatic activity and biological functions.
- Constitutively open TG2 mutants exhibit cytotoxicity towards cancer cells, suggesting stabilization of this state as a therapeutic approach.
Purpose of the Study:
- To elucidate the conformational states of Transglutaminase 2 (TG2) using advanced structural techniques.
- To investigate the mechanism of action of a novel TG2 inhibitor, LM11, on TG2 conformation.
- To explore the potential of stabilizing the open TG2 conformation for cancer therapy.
Main Methods:
- Static and time-resolved small-angle X-ray scattering (SAXS) to analyze TG2 structure and dynamics.
- Single-particle cryoelectron microscopy (cryo-EM) for high-resolution structural determination.
- Biochemical assays to assess TG2 activity and inhibitor efficacy.
Main Results:
- Guanine nucleotides stabilize a monomeric closed conformation of TG2, while calcium ions promote an open, oligomeric state.
- A TG2 mutant adopting an open conformation binds nucleotides via a distinct mechanism compared to wild-type TG2.
- The TG2 inhibitor LM11 enhances calcium binding, stabilizing the cytotoxic open conformation irreversibly and demonstrating potent glioblastoma cell killing.
Conclusions:
- TG2 exhibits more complex conformational dynamics than previously understood.
- LM11 effectively stabilizes a cytotoxic open conformation of TG2, independent of guanine nucleotides.
- Stabilizing the open TG2 conformation with LM11 presents a promising therapeutic strategy against aggressive cancers like glioblastoma.
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