Midline 1 controls polarization and migration of murine cytotoxic T cells

Abstract

Midline 1 (MID1) is a microtubule-associated ubiquitin ligase that regulates protein phosphatase 2 A levels. Loss-of-function mutations in MID1 lead to the human X-linked Opitz G/BBB (OS) syndrome characterized by defective midline development during embryogenesis. We have recently shown that MID1 is strongly up-regulated in murine cytotoxic T lymphocytes (CTLs), and that it has a significant impact on exocytosis of lytic granules and the killing capacity of CTLs. The aims of the present study were to determine the localization of MID1 in migrating CTLs, and to investigate whether MID1 affects CTL polarization and migration. We found that MID1 mainly localizes to the uropod of migrating CTLs and that it has a substantial impact on CTL polarization and migration in vitro. Furthermore, analysis of contact hypersensitivity responses supported that MID1 controls effector functions of CTLs in hapten-challenged skin in vivo. These results provide significant new knowledge on the role of MID1 in CTL biology.

Proteomics reveals signal peptide features determining the client specificity in human TRAP-dependent ER protein import

“…Additional proteins that were positively affected by both depletions were the two cytosolic proteins helicase-like transcription factor (HLTF) and Midline 1 (MID1) (Supplementary Data 4 , 6 , 7 ). Interestingly, both proteins have ubiquitin-ligase activity and were previously connected to cell migration and collagen biogenesis, respectively 34 , 35 . There was no indication for activation of the unfolded protein response (UPR) in the course of the 96 h knock-down, i.e., related terms did not come up as enriched GO terms in the analysis of the positively affected proteins and typical UPR-regulated genes such as HSPA5, HSPB1 , and HYOU1 were not up-regulated (Supplementary Data 7 , see the following paragraph on validation of TRAP clients).…”

Stage-specific roles for Zmiz1 in Notch-dependent steps of early T-cell development

“…We used a specific anti-Notch1 antibody 25 to separate Zmiz1-regulated genes into Notch1-dependent and Notch1-independent classes. Many of the top-ranked Notch1independent genes based on fold change (supplemental Table 10) have no role in T-cell development based on knockout mouse studies, [51][52][53][54][55][56][57][58][59][60][61] but some do. 62,63 We note that none of the top 20 Notch1-regulated genes (supplemental Table 11) have been shown to contribute to the DN-DP transition.…”

MID2 can substitute for MID1 and control exocytosis of lytic granules in cytotoxic T cells

“…Interestingly, although we have demonstrated that MID1 plays important roles in CTL function (4,5), OS patients have not been reported to be more susceptible to viral infections. Most clinical reports describe the developmental anatomical defects, which are the main features of OS.…”

“…In human, almost 70 members of the TRIM family have been identified. These proteins are implicated in a plethora of cellular processes including immune responses (3)(4)(5). As other members of the TRIM family, MID1 and MID2 are E3 ubiquitin ligases (6)(7)(8).…”

“…Thus, the microtubule cytoskeleton plays a key role in directional secretion of lytic granules and thereby in CTL-mediated killing (22). We have recently shown that MID1 is strongly upregulated in murine CTL, and that it controls migration, exocytosis of lytic granules and the killing capacity of CTL (4,5). Accordingly, CTL from MID1 knock-out (MID1 À/À ) mice have a 25-30% reduction in exocytosis of lytic granules and cytotoxicity compared to CTL from wild-type (WT) mice (4).…”