Anti-KDEL-ER Marker monoclonal antibody

The survival of naive T cells is believed to require signals from TCR-pMHC interactions and cytokines such as IL-7. In contrast, signals that negatively impact naive T cell survival are less understood. We conducted a forward genetic screening of mice and found a mutant mouse line with reduced number of naive T cells (T-Red mice). T-Red mice have a point mutation in the Kdelr1 gene, and their naive T cells show enhanced integrated stress response (ISR), which eventually induces their apoptosis. Therefore, naive T cells require a KDEL receptor-mediated mechanism that efficiently relieves cellular stress for their survival in vivo. Interestingly, naive T cells expressing TCR with higher affinity/avidity to self-antigens survive in T-Red mice, suggesting the possible link between TCR-mediated survival and ISR-induced apoptosis. In this article, we discuss the regulation of naive T cell homeostasis, keeping special attention on the ISR and TCR signal.

CREB3 is an ER membrane-bound transcription factor; however, post-translational regulation of CREB3, including expression, processing, and activation, is not fully characterized. We therefore constructed several types of mouse CREB3 expression genes and elucidated their expression in Neuro2a cells by treatment with stimuli and co-transfection with genes associated with ER-Golgi homeostasis, such as mutant Sar1 [H79G], GRP78, and KDEL receptor 1 (KDELR1). Interestingly, treatment of Neuro2a cells expressing Flag-tagged full-length CREB3 with monensin and nigericin induced the expression of the approximately 50 kDa N-terminal fragment; however, its cleavage was not parallel to the levels of GADD153 and LC3-II. Co-transfection of full-length CREB3 together with Sar1 [H79G], GRP78, or KDELR1 showed that only Sar1 [H79G] induced expression of the cleaved form, and KDELR1 dramatically decreased the expression of the full-length form. Accordingly, Sar1 [H79G]- and KDELR1-overexpression influenced GAL4-CREB3-dependent luciferase activities. To understand the activation of CREB3 under more pathophysiological conditions, we focused on the effect of metal ions on CREB3 cleavage in Neuro2a cells. Among the six metal ions we tested, only copper ion stabilized full-length CREB3 expression. Copper ion also increased its N-terminal form and GAL4-CREB3-dependent luciferase activity, which was accompanied by the increase in the ubiquitinated proteins in Neuro2a cells. Taken together, CREB3 expression is regulated by multiple ER-Golgi resident factors in a post-translational manner, but its processing is not directly associated with ER stress and autophagic dysfunction. This finding is especially true for the unique action of the copper ion on CREB3 stabilization and processing in parallel to aberration of ubiquitin-proteasome system, which might provide new insights into understanding the mechanisms of intractable disorders.