LMAN1 (ERGIC-53) promotes trafficking of neuroreceptors

The endoplasmic reticulum-Golgi intermediate compartment protein-53 (ERGIC-53, aka LMAN1), which cycles between the endoplasmic reticulum (ER) and Golgi, is a known cargo receptor for a number of soluble proteins. However, whether LMAN1 plays a role as a trafficking factor in the central nervous system is largely unknown. Here, we determined the role of LMAN1 on endogenous protein levels of the Cys-loop superfamily of neuroreceptors, including gamma-aminobutyric acid type A receptors (GABA_ARs), 5-hydroxytryptamine (serotonin) type 3 (5-HT₃) receptors, and nicotinic acetylcholine receptors (nAChRs). Knockdown of LMAN1 reduces the surface trafficking of endogenous β3 subunits of GABA_ARs in mouse hypothalamic GT1-7 neurons. Furthermore, Western blot analysis of brain homogenates from LMAN1 knockout mice demonstrated that loss of LMAN1 decreases the total protein levels of 5HT₃A receptors and γ2 subunits of GABA_ARs. LMAN1 knockout regulates the ER proteostasis network by upregulating ERP44 without changing calnexin levels. Interestingly, despite the critical role of the glycan-binding function of LMAN1 in its other known cargo clients, LMAN1 interacts with GABA_ARs in a glycan-independent manner. In summary, LMAN1 is a trafficking factor for certain neuroreceptors in the central nervous system. This is the first report of LMAN1 function in membrane protein trafficking.

ERP44 inhibits human lung cancer cell migration mainly via IP3R2

Cancer cell migration is involved in tumour metastasis. However, the relationship between calcium signalling and cancer migration is not well elucidated. In this study, we used the human lung adenocarcinoma A549 cell line to examine the role of endoplasmic reticulum protein 44 (ERP44), which has been reported to regulate calcium release inside of the endoplasmic reticulum (ER), in cell migration. We found that the inositol 1,4,5-trisphosphate receptors (IP3Rs/ITPRs) inhibitor 2-APB significantly inhibited A549 cell migration by inhibiting cell polarization and pseudopodium protrusion, which suggests that Ca2+ is necessary for A549 cell migration. Similarly, the overexpression of ERP44 reduced intracellular Ca2+ release via IP3Rs, altered cell morphology and significantly inhibited the migration of A549 cells. These phenomena were primarily dependent on IP3R2 because wound healing in A549 cells with IP3R2 rather than IP3R1 or IP3R3 siRNA was markedly inhibited. Moreover, the overexpression of ERP44 did not affect the migration of the human neuroblastoma cell line SH-SY5Y, which mainly expresses IP3R1. Based on the above observations, we conclude that ERP44 regulates A549 cell migration mainly via an IP3R2-dependent pathway.

The regulatory network of lncRNA DLX6-AS1/miR-149-5p/ERP44 is possibly related to the progression of preeclampsia

BACKGROUND

Long noncoding RNA DLX6 antisense RNA 1 (DLX6-AS1) has been reported to be involved in various human diseases, however, its potential role in the pathogenesis of preeclampsia (PE) has not been fully explored.

METHODS

The levels of DLX6-AS1, microRNA-149-5p (miR-149-5p) and endoplasmic reticulum protein 44 (ERP44) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Some clinicopathological parameters of PE were statistically analyzed. The cell proliferation, invasion and angiogenesis were assessed by methylthiazolyldiphenyl-tetrazolium bromide (MTT), transwell and tube formation assays, respectively. Levels of all protein were detected by western blot. The target relationship was predicted by StarBase v2.0 and confirmed by dual-luciferase reporter assay.

RESULTS

Higher levels of DLX6-AS1 and ERP44, lower level of miR-149-5p were observed in PE placenta tissues. Compared with PE group with low DLX6-AS1 expression, the systolic blood pressure, diastolic blood pressure and proteinuria levels in the group with high DLX6-AS1 expression were higher, and the infant body weight level was lower. The role of miR-149-5p on these clinicopathological parameters of PE patients was opposite to that of DLX6-AS1, while ERP44 had the same effect as DLX6-AS1. Besides, DLX6-AS1 directly targeted miR-149-5p and miR-149-5p targeted ERP44. The inhibitory impact of DLX6-AS1 overexpression or ERP44 overexpression on proliferation and invasion of trophoblast cells as well as angiogenesis of HUVEC cells was reversed by up-regulating miR-149-5p. We also found that DLX6-AS1 could enhance ERP44 expression by sponging miR-149-5p.

CONCLUSION

DLX6-AS1 inhibited proliferation and invasion of trophoblast cells, and suppressed angiogenesis of HUVEC cells by miR-149-5p/ERP44 pathway.

ERP44 could serve as a bridge mediating prognosis and immunity for glioma via single-cell and bulk RNA-sequencing

BACKGROUND

There was evidence that ERP44 played vital roles in a variety of cancers. However, currently, ERP44 was rarely mentioned in gliomas. Therefore, we firstly integrated proteomics, bulk, as well as single-cell RNA-sequencing (scRNA-seq) to study the possible functions of ERP44 in glioma patients.

METHODS

From online databases, we obtained bulk RNA-seq, scRNA-seq, and proteomic data of ERP44 in gliomas and verified the expression of ERP44 by qRT-PCR. Then, the Noman diagram, gene set enrichment analysis (GSEA), and univariate/multivariate Cox regression analysis were all carried out in turn. Further discussions were also conducted regarding tumor immunity and ERP44 expression.

RESULTS

ERP44 in glioma tissues was found to be considerably higher than that in normal tissues (P<0.05) in the TCGA dataset, as well as the verification of GSE50161, GSE4290, and qRT-PCR results. High ERP44 expression indicated poorer overall survival (OS) for glioma (P<0.05), and it might also be used to predict gliomas' OS independently (P<0.05). In order to estimate these patients' survival prognosis, a Noman chart was created with effectiveness. According to GSEA analysis, ERP44 might be implicated in five significant pathways in gliomas. The levels of immune cell infiltration of LGG, the tumor immune microenvironments, the immunological checkpoints of LGG, and GBM were all strongly linked with ERP44 in terms of tumor immunity (P<0.05). Further scRNA-seq analysis revealed that ERP44 could be expressed in various cell types, including T cells, Mono/Macrophages, and malignant cells.

CONCLUSIONS

ERP44 was an oncogenic gene in gliomas, serving as a bridge mediating prognosis and immunity.