Deposition of Laminin 5 by Keratinocytes Regulates Integrin Adhesion and Signaling

Abstract

Deposition of laminin 5 over exposed dermal collagen in epidermal wounds is an early event in repair of the basement membrane. We report that deposition of laminin 5 onto collagen switches adhesion and signaling from collagen-dependent to laminin 5-dependent. Ligation of laminin 5 by integrin ␣ 6 ␤ 4 activates phosphoinositide 3-OH-kinase (PI3K) signaling. This activation allows for adhesion and spreading via integrin ␣ 3 ␤ 1 on laminin 5 independent of RhoGTPase, a regulator of actin stress fibers. In contrast, adhesion and spreading on collagen via ␣ 2 ␤ 1 is Rho-dependent and is inhibited by toxin B, a Rho inhibitor. Deposition of laminin 5 and ligation of ␣ 6 ␤ 4 increases PI3K-dependent production of phosphoinositide di-and triphosphates, PI3K activity, and phosphorylation of downstream target protein cJun NH 2 -terminal kinase. Conversely, blocking laminin 5-deposition with brefeldin A, an inhibitor of vesicle transport, or with anti-laminin 5 monoclonal antibodies abolishes the PI3K-dependent spreading mediated by ␣ 3 ␤ 1 and phosphorylation of c-Jun NH 2 -terminal kinase. Studies with keratinocytes lacking ␣ 6 ␤ 4 or laminin 5 confirm that deposition of laminin 5 and ligation by ␣ 6 ␤ 4 are required for PI3K-dependent spreading via ␣ 3 ␤ 1 . We suggest that deposition of laminin 5 onto the collagen substratum, as in wound repair, enables human foreskin keratinocytes to interact via ␣ 6 ␤ 4 and to switch from a RhoGTPase-dependent adhesion on collagen to a PI3K-dependent adhesion and spreading mediated by integrin ␣ 3 ␤ 1 on laminin 5.Laminin 5 is a major adhesive component of many epithelial basement membranes (BMs) 1 and is secreted by epithelial cells in tissue and in culture. Injury of epidermis activates transcription and deposition of laminin 5 into the provisional BM by the leading keratinocytes of the epidermal outgrowth that migrates into the wound bed (1-4). The activated expression of laminin 5 occurs within hours after injury and prior to expression of laminin 10/11 or type VII collagen, attesting to the import of laminin 5 for tissue repair. Deposition of laminin 5 over the exposed collagen and fibronectin is required for the repair of the BM and for re-establishing anchorage of the epithelium to the BM via integrin ␣ 6 ␤ 4 in hemidesmosomes (5-9). Here, we have examined the function of laminin 5 deposited onto exposed dermal collagen in regulating adhesion and signaling in epidermal outgrowths.Based on in vivo and in vitro studies, keratinocyte interactions with laminin 5 are mediated by integrins ␣ 6 ␤ 4 and ␣ 3 ␤ 1 ; interactions with ␣ 6 ␤ 4 mediate anchorage, whereas interactions with ␣ 3

Laminin-332 promotes the invasion of oesophageal squamous cell carcinoma via PI3K activation

“…Laminin-332 has been reported to interact with integrin a3b1 or a6b4 and activate many signal mediators such as PI3K, focal adhesion kinase, protein kinase C, Rac, ERK, JNK and nuclear factor kB, leading to enhanced cell migration and invasion (Nguyen et al, 2000;Kariya and Miyazaki, 2004;Nikolopoulos et al, 2005). In particular, the importance of PI3K activation induced by laminin-332 during carcinogenesis or tumour invasion has been recently suggested (Marinkovich, 2007;Waterman et al, 2007).…”

“…In several types of carcinomas, laminin-332 has been reported to be highly expressed and to correlate well with poor patient prognosis (Pyke et al, 1995;Soini et al, 1996;Koshikawa et al, 1999;Matta et al, 1999;Ono et al, 1999;Yamamoto et al, 2001;Fukai et al, 2005). Laminin-332 is known to support cellular survival, proliferation and migration by activating many signal mediators through the ligation with a3b1 and a6b4 integrin, and to have important roles in tumour invasion and metastasis (Nguyen et al, 2000;Kariya and Miyazaki, 2004;Nikolopoulos et al, 2005). Particularly, the phosphatidylinositol 3-kinase (PI3K) activation induced by laminin-332 during carcinogenesis or tumour invasion has been highlighted (Marinkovich, 2007;Waterman et al, 2007).…”

Integrin α6β4-erbB2 Complex Inhibits Haptotaxis by Up-regulating E-cadherin Cell-Cell Junctions in Keratinocytes

“…Importantly, Geuijen and Sonnenberg (40) showed that ␣6␤4-triggered motility inhibition was not simply due to increased adhesion to Ln-5 but was a result of increased stability of the interaction between ␣6␤4 and Ln-5. Thus, ␣6␤4-triggered simultaneous up-regulation of both cell-ECM and cell-cell adhesion may result in an adhesive, non-migratory phenotype and may explain the observation that Ln-5 can guide keratinocytes to switch from a migratory-to a dormant, integrated epithelial phenotype (11,41). Concerted substrate-and intercellular adhesion regulation is a prerequisite for tissue rearrangement during morphogenesis or remodeling (42).…”

ΔNp63α Expression Is Regulated by the Phosphoinositide 3-Kinase Pathway

“…This regulation of PI3K by integrin signaling has particular implications for ⌬Np63␣ expression. ⌬Np63␣ expression in the epidermis is limited to the basal layer of keratinocytes, which maintain contact with the basement membrane (12,13); certain integrin signaling pathways are highly active in these cells (32,53). Integrin-mediated activation of the PI3K pathway, therefore, may be partly responsible for the observed distribution of ⌬Np63␣ expression in the epidermis.…”