期刊
MOLECULAR AND CELLULAR BIOLOGY
卷 21, 期 1, 页码 148-155出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/MCB.21.1.148-155.2001
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资金
- Telethon [E.0872] Funding Source: Medline
Transglutaminase 2 (TGase 2), or tissue transglutaminase, catalyzes either epsilon-(gamma -glutamyl)lysine or N-1,N-8-(gamma -glutamyl)spermidine isopeptide bonds. TGase 2 expression has been associated with apoptosis, and it has been proposed that its activation should lead to the irreversible assembly of a cross-linked protein scaffold in dead cells. Thus, TGase 2-catalyzed protein polymerization contributes to the ultrastructural changes typical of dying apoptotic cells; it stabilizes the integrity of the apoptotic cells, preventing the release of harmful intracellular components into the extracellular space and, consequently, inflammation and scar formation. In order to perform a targeted disruption of the enzyme, me prepared a construct deleting part of exons 5 and 6, containing the active site, and intron 5. Complete absence of TGase 2 was demonstrated by reverse transcription-PCR and Western blot analysis, TGase activity measured on liver and thymus extracts showed, however, a minimal residual activity in TGase 2(-/-) mice, PCR analysis of mRNA extracted from the same tissues demonstrated that at least TGase 1 (normally present in the skin) is also expressed in these tissues and contributes to this residual activity, TGase 2(-/-) mice shelved no major developmental abnormalities, and histological examination of the major organs appeared normal, Induction of apoptosis ex vivo in TGase 2(-/-) thymocytes (by CD95, dexamethasone, etoposide, and H2O2) and in vitro on TGase 2(-/-) mouse embryonal fibroblasts (by retinoids, UV, and H2O2) showed no significant differences. A reduction in cross-linked apoptotic bodies with a modestly increased release of lactate dehydrogenase has been detected in some cases. Together our results show that TGase 2 is not a crucial component of the main pathway of the apoptotic program. It is possible that the residual enzymatic activity, due to TGase 1 or redundancy of other still-unidentified TGases, can compensate for the lack of TGase 2.
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