Substantial evidence implicates EGF-like growth factors (GFs) in promoting the survival, proliferation, migration and invasiveness of normal and malignant epithelial cells. Several different signaling pathways have been shown to promote shedding of membrane-bound EGF-like GFs. Our published data demonstrate that metalloproteinases (MPs) are a major stimulus for ErbB signaling, ERK activation and subsequent gene expression in human skin organ culture. Our preliminary data indicate that MPs are required for autocrine ERK activation in normal human keratinocytes (NHK). They also demonstrate that MP inhibitors block proliferation and wound-induced migration of NHK, and that different ligands appear to be involved in LPA stimulation, autocrine proliferation, and wound-induced migration of NHK. Together, these data indicate that autocrine keratinocyte (KC) signaling requires context-dependent cleavage of membrane-bound ErbB ligands by MPs. The MP(s) involved in transactivating ErbB receptors in skin and KCs have not yet been elucidated. Several members of the ADAM family are strongly implicated in ectodomain processing of various membrane-bound proteins. ADAM10 was recently shown to mediate the basal as well as G protein-coupled receptors (GPCR)-stimulated activation of EGF receptors in mammary epithelial cells. Our preliminary data indicate that ADAM10 is abundantly expressed in NHK, and that expression of the active form of ADAM10 correlates with EGF-independent migration and ERK activation. Based on these observations, we hypothesize that KCs utilize ADAM10 to catalyze shedding of one or more transmembrane EGF-like GF precursors in a context-dependent manner, leading to stimulus-specific KC responses. To test this hypothesis, we propose the following specific aims:
Specific Aim 1 : To (a) determine which ErbB receptor ligands are shed from KC via MP-dependent proteolysis in three cellular contexts (LPA stimulation, autocrine proliferation, and wound-induced migration), and (b) to elucidate the context-dependent functions of the various autocrine ErbB ligands identified in Aim la.
Specific Aim 2 determines whether and in which contexts ADAM10 is involved in the shedding of ErbB ligands in human KCs.
|Lambert, Sylviane; Swindell, William R; Tsoi, Lam C et al. (2017) Dual Role of Act1 in Keratinocyte Differentiation and Host Defense: TRAF3IP2 Silencing Alters Keratinocyte Differentiation and Inhibits IL-17 Responses. J Invest Dermatol 137:1501-1511|
|Molinuevo, R; Freije, A; de Pedro, I et al. (2017) FOXM1 allows human keratinocytes to bypass the oncogene-induced differentiation checkpoint in response to gain of MYC or loss of p53. Oncogene 36:956-965|
|Li, Yong; Stoll, Stefan W; Sekhon, Sahil et al. (2016) Transgenic expression of human amphiregulin in mouse skin: inflammatory epidermal hyperplasia and enlarged sebaceous glands. Exp Dermatol 25:187-93|
|Stoll, Stefan W; Stuart, Philip E; Lambert, Sylviane et al. (2016) Membrane-Tethered Intracellular Domain of Amphiregulin Promotes Keratinocyte Proliferation. J Invest Dermatol 136:444-452|
|Stoll, S W; Stuart, P E; Swindell, W R et al. (2016) The EGF receptor ligand amphiregulin controls cell division via FoxM1. Oncogene 35:2075-86|
|Stoll, Stefan W; Rittie, Laure; Johnson, Jessica L et al. (2012) Heparin-binding EGF-like growth factor promotes epithelial-mesenchymal transition in human keratinocytes. J Invest Dermatol 132:2148-57|
|Johnston, Andrew; Gudjonsson, Johann E; Aphale, Abhishek et al. (2011) EGFR and IL-1 signaling synergistically promote keratinocyte antimicrobial defenses in a differentiation-dependent manner. J Invest Dermatol 131:329-37|
|Stoll, Stefan W; Johnson, Jessica L; Bhasin, Ajay et al. (2010) Metalloproteinase-mediated, context-dependent function of amphiregulin and HB-EGF in human keratinocytes and skin. J Invest Dermatol 130:295-304|
|Stoll, Stefan W; Johnson, Jessica L; Li, Yong et al. (2010) Amphiregulin carboxy-terminal domain is required for autocrine keratinocyte growth. J Invest Dermatol 130:2031-40|