Protein diaphanous homolog 1 (Diaph1) promotes myofibroblastic activation of hepatic stellate cells by regulating Rab5a activity and TGFβ receptor endocytosis

Abstract

TGFβ induces the differentiation of hepatic stellate cells (HSCs) into tumor‐promoting myofibroblasts but underlying mechanisms remain incompletely understood. Because endocytosis of TGFβ receptor II (TβRII), in response to TGFβ stimulation, is a prerequisite for TGF signaling, we investigated the role of protein diaphanous homolog 1 (known as Diaph1 or mDia1) for the myofibroblastic activation of HSCs. Using shRNA to knockdown Diaph1 or SMIFH2 to target Diaph1 activity of HSCs, we found that the inactivation of Diaph1 blocked internalization and intracellular trafficking of TβRII and reduced SMAD3 phosphorylation induced by TGFβ1. Mechanistic studies revealed that the N‐terminal portion of Diaph1 interacted with both TβRII and Rab5a directly and that Rab5a activity of HSCs was increased by Diaph1 overexpression and decreased by Diaph1 knockdown. Additionally, expression of Rab5aQ79L (active Rab5a mutant) increased whereas the expression of Rab5aS34N (inactive mutant) reduced the endosomal localization of TβRII in HSCs compared to the expression of wild‐type Rab5a. Functionally, TGFβ stimulation promoted HSCs to express tumor‐promoting factors, and α‐smooth muscle actin, fibronection, and CTGF, markers of myofibroblastic activation of HSCs. Targeting Diaph1 or Rab5a suppressed HSC activation and limited tumor growth in a tumor implantation mouse model. Thus, Dipah1 and Rab5a represent targets for inhibiting HSC activation and the hepatic tumor microenvironment.

PD-L1 promotes myofibroblastic activation of hepatic stellate cells by distinct mechanisms selective for TGF-β receptor I versus II

“…To determine TbRII-HA/LAMP-1 co-localization in HSCs, HSCs serum-starved overnight were incubated with TGFb1 (5 ng/mL) and collected at different time points, 0, 15, and 45 min, for IF. Image acquisition and analysis of TbRII-HA/LAMP-1 co-localization were done as we previously described (Liu et al, 2013(Liu et al, , 2020.…”

Fibrogenic signals persist in DAA-treated HCV patients after sustained virological response

“…So far, we focused on the protein diaphanous homolog 1 (DIAPH1) belonging to the family of formin proteins and recently described to promote myofibroblastic activation of HSCs. [36][37][38] Indeed, this protein was found as the most upregulated in T0, and worthy of note, also in T6 samples despite viral clearance. With the intent to validate this evidence by means of a different approach and in order to extend it to a broader patient group, western blot analysis was performed on 14 HD and 20 longitudinally enrolled HCV patient (T0 and T6) EV samples.…”

“…Moreover, DIAPH1 inactivation suppresses HSCs' tumor-promoting effects in a tumor implantation mouse model. 36 With respect to other HCV-induced EV hit proteins that could be potential biomarkers, it is worth noting that ANXA3 and ACTR2 have previously been described as poor prognostic signatures in HCV cirrhotic patients. 44 This evidence strongly supports the notion of persistent fibrogenic/pathogenic EV informational content despite viral clearance.…”

Atractylenolide-I Sensitizes Triple-Negative Breast Cancer Cells to Paclitaxel by Blocking CTGF Expression and Fibroblast Activation

“…found that CTGF is required for the activation of cancer-associated fibroblasts in a murine model of melanoma ( 56 ). As a downstream effector of the profibrotic molecule TGF-β, CTGF can promote the differentiation of hepatic stellate cells into tumor-promoting myofibroblasts ( 33 ). All these observations support our findings.…”

“…CTGF can regulate the expression of antiapoptotic genes in tumor cells ( 32 ). CTGF can also induce a variety of cells to transform into CAFs in the tumor microenvironment ( 33 – 36 ). CTGF expression is increased in CAFs and negatively correlated with disease-free survival ( 35 ).…”