Loss of Gab1 adaptor protein in hepatocytes aggravates experimental liver fibrosis in mice

Abstract

Grb2-associated binder 1 (Gab1) adaptor protein amplifies signals downstream of a broad range of growth factors/receptor tyrosine kinases. Although these signals are implicated in liver fibrogenesis, the role of Gab1 remains unclear. To elucidate the role of Gab1, liver fibrosis was examined in hepatocyte-specific Gab1-conditional knockout (Gab1CKO) mice upon bile duct ligation (BDL). Gab1CKO mice developed exacerbated liver fibrosis with activation of hepatic myofibroblasts after BDL compared with control mice. The antifibrotic role of hepatocyte Gab1 was further confirmed by another well-established mouse model of liver fibrosis using chronic injections of carbon tetrachloride. After BDL, Gab1CKO mice also displayed exacerbated liver injury, decreased hepatocyte proliferation, and enhanced liver inflammation. Furthermore, cDNA microarray analysis was used to investigate the potential molecular mechanisms of the Gab1-mediated signal in liver fibrosis, and the fibrosis-promoting factor chemokine (C-C motif) ligand 5 ( Ccl5) was identified as upregulated in the livers of Gab1CKO mice following BDL. Interestingly, in vitro studies using primary hepatocytes isolated from control and Gab1CKO mice revealed that the loss of Gab1 resulted in increased hepatocyte CCL5 synthesis upon lipopolysaccharide stimulation. Finally, pharmacological antagonism of CCL5 reduced BDL-induced liver fibrosis in Gab1CKO mice. In conclusion, our results demonstrate that hepatocyte Gab1 is required for liver fibrosis and that hepatocyte CCL5 could be an important contributor to this process. Thus, we present a novel antifibrotic function of hepatocyte Gab1 in liver fibrogenesis.

Increased expression of Forkhead box M1 transcription factor is associated with clinicopathological features and confers a poor prognosis in human hepatocellular carcinoma

“…Total RNA was extracted using a Qiagen (Hilden, Germany) QIAshredder and an RNA‐easy Mini kit according to the manufacturer's instructions. Reverse transcription–polymerase chain reaction (RT‐PCR) and real‐time PCR were carried out as described previously . The Quantitect gene assay kit (Qiagen) was used for the analysis of human FoxM1, and glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH).…”

Gab1 adaptor protein acts as a gatekeeper to balance hepatocyte death and proliferation during acetaminophen‐induced liver injury in mice

“…Hepatocytes were isolated from control and Gab1 CKO mice using the two‐step pronase‐collagenase perfusion method and cultured as described . Hepatocyte preparations with viability of 90% or higher, as determined by trypan blue exclusion, were used for experiments.…”

“…We previously showed that Gab1 regulates mouse embryo development through these pathways in vivo . More recently, we demonstrated that in hepatocytes Gab1 is essential for protection against liver fibrogenesis in mice . Furthermore, others have shown that Gab1 promotes hepatocyte proliferation after partial hepatectomy in mice, indicating that Gab1 is crucial for the repair process following liver injury.…”

Stromal and immune cells in gut fibrosis: the myofibroblast and the scarface

“…FGF-1 is able to decrease collagen production and α-SMA expression on fibroblasts, partially inhibit TGF-β and reverse TGF-β-induced EMT [123,124], Grb2-associated binder 1 (Gab1) adaptor protein is a docking protein that interacts with receptor tyrosine kinases, amplifying growth factor signals [125]. In an animal model of liver fibrosis, Kizu et al showed that Gab1-conditional knockout mice developed severe liver fibrosis, indicating a possible antifibrotic or homeostatic role of Gab-1 [126]. …”