033 Regulation of TGF‐β Responses by a Novel Accessory TGF‐β Receptor in Human Keratinocytes

Abstract

The potential of TGF‐β isoforms to regulate wound healing and scarring is well documented in animal models. Since TGF‐β action is likely to be regulated at the level of its cell surface receptors, we analyzed TGF‐β receptor profiles and regulation of TGF‐β signaling in human keratinocytes. We identified a novel cell surface TGF‐β1 binding protein of 150 kDa (r150) on human keratinocytes that interacts with the TGF‐β signaling receptors. Further characterization of r150 demonstrated that it is a GPI‐anchored protein, that it can be released from the cell surface by an endogenous phospholipase C, and that the released form can bind to TGF‐β1. Recent cloning of r150 revealed it to be a novel protein of 1428 amino acids. Our objective was to determine the functional significance of r150 in regulating TGF‐β responses in keratinocytes.Affinity labeling of keratinocytes overexpressing r150 cDNA and immunoprecipitation stud‐ies using anti‐r150 antibodies show that the cloned cDNA represents r150. Importantly, over expression of r150 results in inhibition of TGF‐β1‐induced Smad 2 and Smad 3 phosphorylation, gene transcriptional activity, and keratinocyte migration. In contrast, loss of r150 function using antisense morpholino oligos of r150 leads to enhanced Smad 2 and Smad 3 phosphorylation, gene transcriptional activity and proliferation of keratinocytes. In summary, our results demonstrate that r150 is a potent inhibitor of TGF‐β signaling in keratinocytes, and that it may have potential therapeutic value in modulating TGF‐β action in human diseases where TGF‐β plays a pathophysiological role. As such, r150 may be of use in reducing hypertrophic scarring, and an r150 antagonist may promote wound healing.