Glycosylation Regulation by TMEM230 in Aging and Autoimmunity

Abstract

Aging is often a choice between developing cancer or autoimmune disorders, often due in part to loss of self-tolerance or loss of immunological recognition of rogue-acting tumor cells. Self-tolerance and cell recognition by the immune system are processes very much dependent on the specific signatures of glycans and glycosylated factors present on the cell plasma membrane or in the stromal components of tissue. Glycosylated factors are generated in nearly innumerable variations in nature, allowing for the immensely diverse role of these factors in aging and flexibility necessary for cellular interactions in tissue functionality. In previous studies, we showed that differential expression of TMEM230, an endoplasmic reticulum (ER) protein was associated with specific signatures of enzymes regulating glycan synthesis and processing and glycosylation in rheumatoid arthritis synovial tissue using single-cell transcript sequencing. In this current study, we characterize the genes and pathways co-modulated in all cell types of the synovial tissue with the enzymes regulating glycan synthesis and processing, as well as glycosylation. Genes and biological and molecular pathways associated with hallmarks of aging were in mitochondria-dependent oxidative phosphorylation and reactive oxygen species synthesis, ER-dependent stress and unfolded protein response, DNA repair (UV response and P53 signaling pathways), and senescence, glycolysis and apoptosis regulation through PI3K-AKT-mTOR signaling have been shown to play important roles in aging or neurodegeneration (such as Parkinson's and Alzheimer's disease). We propose that the downregulation of TMEM230 and RNASET2 may represent a paradigm for the study of age-dependent autoimmune disorders due to their role in regulating glycosylation, unfolded protein response, and PI3K-AKT-mTOR signaling.

Keywords: PI3K-AKT-mTOR signaling; Parkinson’s and Alzheimer’s disease; RNASET2; TMEM230 (C20orf30); aging; autoimmunity rheumatoid arthritis; endoplasmic reticulum unfolded protein response; glycosylation; transcriptomic single cell sequencing.

Figure 1

Osteoarthritis (OA) and rheumatoid arthritis (RA) synovial tissue transcriptomic map clustered by cell type. OA and RA high-resolution visualization of synovial tissue composition obtained by Uniform Manifold Approximation and Projection (UMAP) plot of synovial tissue cell type after integrating 3 OA (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE152805, accessed on 30 December 2024) and 4 RA (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE200815, accessed on 30 December 2024) datasets. Different clusters of cells were indicated by different colors according to the expression of representative specific markers as previously described in Angeli et al., 2025 [6] and Abeni et al., 2024 [7].

Figure 2

Box plot graphical visualization of the expression profile of the TMEM230 in OA and RA. The y-axis represents the expression level. p-value < 0.05 was calculated by the Kolmogorov Smirnov (K-S) test. TMEM230 expression is downregulated in all cell types from RA patients compared to OA. TMEM230 expression is very low or not detected in RA patient immune system cells (see DC, PDC and B, T and natural killer cells) compared to OA, suggesting that loss of TMEM230 promotes autoimmune features associated with RA patients. TMEM230 expression levels were previously identified downregulated in RA as described in Angeli et al., 2025 [6].

Figure 3

Box plot graphical visualization of the expression profile of the RNASET2 in OA (left panel, showing cell types with highest expression of RNASET2) and in a RA or OA comparative analysis (right panel). The y-axis represents the expression level. p-value < 0.05 was calculated by the Kolmogorov Smirnov (K-S) test. RNASET2 was previously identified as downregulated as described in Angeli et al., 2025 [6].

Figure 4

Gene and biological pathways differentially expressed between RA and OA patient synovial tissue macrophages may have a role in age-dependent autoimmunity (see Supplementary Materials). Different clusters of cells were identified and indicated by different colors according to the expression of representative specific markers as described in Figure 1, Angeli et al., 2025 [6] and Abeni et al., 2024 [7]. Red circle indicates the macrophage cell containing cluster.

Figure 5

Gene and biological pathways differentially expressed between RA and OA patient synovial tissue associated blood vessel cells that may have a role in age-dependent autoimmunity (see Supplementary Materials). Different colors are described in Figure 1, Angeli et al., 2025 [6] and Abeni et al., 2024 [7]. Red circle indicates blood vessel cells associated with synovial tissue.

Figure 6

Gene and biological pathways differentially expressed between RA and OA patient synovial tissue-associated immune system cells that may have a role in age-dependent autoimmunity (see Supplementary Materials). Different colors are according to Figure 1,Angeli et al., 2025 [6] and Abeni et al., 2024 [7]. Red circle indicates the different immune system cells associated with the synovial tissue.

Figure 7

Gene and biological pathways differentially expressed between RA and OA patient synovial tissue fibroblast cells that may have a role in age-dependent autoimmunity (see Supplementary Materials). Different colors are described in Figure 1 and Angeli et al., 2025 [6] and Abeni et al., 2024 [7]. Red circle indicates different types of synovial fibroblast cells of the synovial tissue.

Figure 8

Super-resolution imaging of phalloidin and Hoechst in U87-MG cells of native levels of TMEM230 (green) (panel (A), labeled as GFP mRNA Lenti virus control) and in which TMEM230 expression was upregulated (panel (B)). Images were collected by using a Stellaris 8 Falcon τ-STED microscope. The Hoechst dye used for staining (blue) the nucleus was excited at 440 nm, and its emission was collected in the range of 448–520 nm. Alexafluor594 detection indicates expression of phalloidin (red) (590 nm and the STED laser, and emission was collected in the range of 600–700 nm). Antibody staining for phalloidin is performed as described in Cocola 2021.

Figure 9

Major physiological functions of TMEM230 endoplasmic reticulum dependent regulation of glycosylation.

Figure 10

Possible pathological roles of aberrant regulation of glycan processing enzymes by TMEM230 in aging (see Supplementary Materials and Figure 4, Figure 5, Figure 6 and Figure 7).