Fig 2: TXNDC5 promotes fibrogenesis by enhancing TGFBR1 protein stability via its PDI activity.a A cycloheximide chase assay performed in HPF with TXNDC5 knockdown (shTXNDC5) showed accelerated degradation of TGFBR1 protein, comparing to control (shScr) (n = 4 biologically independent samples per group). b Overexpression of TXNDC5 slowed down TGFBR1 protein degradation significantly in HFP (n = 7 biologically independent samples per group). c TXNDC5 depletion-induced downregulation of TGFBR1 protein was partially reversed by the treatment of proteasome inhibitor MG132 (20µM for 48 h) (n = 7 biologically independent samples per group). d, e Overexpression of WT, but not AAA mutant (see text for details), TXNDC5 protein in HPF led to significant upregulation of TGFBR1, ECM (fibronectin and COL1A1) proteins and fibroblast activation markers (aSMA and periostin) (n = 8 biologically independent samples per group) (Data are presented as mean ± SEM, P value determined using two-tailed unpaired t tests. Source data are provided as a Source Data file. OE overexpress, TXNDC5 AAA TXNDC5 mutant lacking its PDI enzyme activity).

Fig 3: TXNDC5 modulates TGFBR1 expression in human lung fibroblasts and mouse lungs.a Immunoblots showed that TGFBR1, but not TGFBR2, was markedly upregulated in control HPF (shScr) following TGFß1 treatment. TXNDC5 knockdown (shTXNDC5) prevented TGFBR1 upregulation induced by TGFß1 treatment completely (n = 6 biologically independent samples per group). b Forced TXNDC5 expression led to marked upregulation of TGFBR1, but not TGFBR2, protein in HPF (n = 12 biologically independent samples per group). c TGFBR1 and COL1A1 proteins were both markedly upregulated in the lung tissues from WT, but not Txndc5-/-, mice 21 days following BLM treatment (WT sham n = 4, WT BLM n = 5, Txndc5-/- sham n = 3, Txndc5-/- BLM n = 5 biologically independent animals). d Representative IF staining and quantification (e) of TGFBR1 in Col1a1-GFPTg and Col1a1-GFPTg*Txndc5-/- mouse lungs with PBS (Sham) or BLM treatment on day 21 (n = 9 fields examined over 3 biologically independent animals per group). TGFBR1 was marked increased and showed strong co-localization with GFP-positive lung fibroblasts in BLM-treated mouse lungs. Global deletion of TXNDC5 prevented the upregulation of TGFBR1 in mouse lungs following BLM treatment (Data are presented as mean ± SEM, P value determined using two-tailed Mann–Whitney U test. Source data are provided as a Source Data file. n.s. non-significant, KD knockdown, OE overexpress, BLM bleomycin, TGFBR1 TGFß receptor type 1, TGFBR2 TGFß receptor type 2).