We therefore hypothesized that an additional target for PCN in li

We therefore hypothesized that an additional target for PCN in liver myofibroblasts is the LAGS. The identity of the LAGS has yet to be determined although it shows similar – but not identical binding characteristics – to a steroid binding activity to which the progesterone receptor membrane component 1 (PGRMC1) may be associated [10–14]. find more There are 2 PGRMC genes in humans and rodents that code for ~28 kDa proteins. The

proteins have a single N-terminal membrane spanning domain and do not show significant homology with other gene super-families such as nuclear receptors [12]. PGRMC1 has been shown to bind haem [13] but it remains contentious as to whether the protein directly binds steroids, as suggested by Peluso et al [14], or is a component of a complex that binds steroids. Our data with the human Fluorouracil nmr PGRMC1 suggest that phosphorylation of the protein or a component of the binding complex may be important for efficient steroid binding and may explain the difficulties of reconstituting steroid binding, when the protein is purified or over-expressed in mammalian cells

[12]. Nonetheless, these data are limited and the identity of the binding protein remains to be unambiguously demonstrated. Recent evidence suggests, however, that PGRMC1 binds to cytochrome P450s and functions to facilitate cytochrome P450-mediated metabolism of sterol biosynthesis [15]. Interestingly, PGRMC1 stably binds to cytochrome P450 51A1 [15], an isoform that has been shown to be expressed in activated human liver myofibroblasts [16]. We therefore hypothesized that PCN mediates its PXR-independent mechanism of inhibiting

myofibroblast trans-differentiation/proliferation via a LAGS/PGRMC interaction. To test this hypothesis, rat PGRMC1 was cloned and expressed and binding of PCN to the protein or a complex containing this protein confirmed. Through a series of established in vitro screens, a putative ligand for rat and human PGRMC1-associated complex – that was not also a PXR activator – was identified and shown to potently inhibit rat and human liver Acesulfame Potassium myofibroblast trans-differentiation and proliferation, in vitro. However, this compound failed to show any anti-fibrogenic activity in an in vivo model of liver fibrosis because the target PGRMC1 was not expressed by myofibroblasts, in vivo. Results The PGRMC1 is expressed in rat and human HSCs and myofibroblasts Quiescent HSCs were isolated from normal rat liver or from histologically normal margins of human liver tissue resected because of the presence of a secondary tumour. When placed in the appropriate culture conditions, these cells trans-differentiate into myofibroblasts, reminiscent of the process that occurs in the liver in response to chronic liver damage [1].

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