Laminin α5 in the keratinocyte basement membrane is required for epidermal–dermal intercommunication (original) (raw)
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Laminin 5 Deposition Promotes Keratinocyte Motility
Experimental Cell Research, 1996
mechanisms are not well understood, it is clear that We examined the role of individual integrins in pro-integrin receptors play crucial roles in cell migration moting human keratinocyte migration. In short-term by interacting with the provisional wound matrix [1, assays on collagen type I-or fibronectin-coated sub-2-6]. Keratinocyte migration is also significantly regustrates, migration was blocked by antibody to the a2 lated by extracellular matrix (ECM) components such integrin and the a5 integrin, respectively. Unexpectas collagens, fibronectin, and laminin [1, 7-9]. edly, antibodies to integrin a3 also significantly inhib-Keratinocyte integrins mediate cell-to-extracellularited cell locomotion on both ligands. Time-course immatrix and possibly cell-to-cell interactions [4, 10-12]. munofluorescence staining revealed that keratinocyte The integrins a2b1 and a3b1 are widely expressed in migration was accompanied by deposition of endogevarious tissues and cultured cells and are especially nous laminin 5. Since a3b1 is a known receptor for abundant in proliferating epithelial tissues [1, 10]. These this ligand, this observation suggested that migrating integrins are components of focal adhesion plaques, keratinocytes use freshly deposited laminin 5 in locowhich associate with actin-containing stress fibers and motion. Indeed, further investigation showed that control motility and adhesion [10, 11, 13]. They also apanti-laminin 5 blocking antibodies effectively inhibpear to be involved in cell-cell interactions [10, 14, 15]. ited keratinocyte motility on both collagen and fibro-By contrast, integrin a6b4 is expressed primarily in epinectin substrates. Furthermore, cell migration on laminin 5-coated substrates was blocked by both anti-a3 thelial and Schwann cells [16]. It is the primary adhesion and anti-laminin 5 antibodies. Laminin 5 did not apreceptor in hemidesmosomes in vivo [3, 12, 17-19] and pear important in the initial attachment of keratinohemidesmosome-like stable anchoring contact structures cytes, since adhesion of cells to collagen type I-or fiin vitro [11], which are not required to contact actinbronectin-coated surfaces was not blocked by anticontaining cytoskeleton. Recent evidence strongly sugbody to a3 integrin or to laminin 5, but could be gests that a3b1 and, to a lesser extent, a6b4 are receptors inhibited by antibody to a2 or a5, respectively. Using for the ECM component laminin 5 (also known as kalinin, an in vitro wound assay, blocking antibodies to a3 inteepiligrin, and nicein) [15, 19-22]. Substantial evidence grin and to laminin 5 also blocked reepithelization of suggests that a3b1 is a promiscuous receptor that can the denuded monolayer. These results show that a3b1 interact with ligands such as collagen, fibronectin, and integrin plays an important role in the migration of laminin 1. It has also been shown that a3b1 can preferenkeratinocytes via their interaction with laminin 5. tially bind certain laminin isoforms, particularly laminin Furthermore, they suggest that cell migration is de-5 (12, 19). pendent not only on exogenous ligands but, impor-Laminin 5, a laminin isoform, is a component of tantly, on endogenously secreted laminin 5. Finally, certain basement membranes synthesized and dethe data are consistent with our earlier finding that laminin 5 is the first extracellular matrix component posited by keratinocytes. Based on a new nomenclato be expressed and deposited by migrating keratinoture, it is composed of a3, b3, and g2 chains [23]. It cytes during wound healing in vivo [1]. ᭧ 1996 Academic was originally detected in the anchoring filaments of Press, Inc. the skin [24, 25]. Laminin 5 has been identified and characterized in cultures of keratinocytes as a disulfide-linked heterotrimer precursor. It has subunits In this study we determined that the attachment of
Human Molecular Genetics, 2011
Nuclear lamins are usually classified as A-type (lamins A and C) or B-type (lamins B1 and B2). A-type lamins have been implicated in multiple genetic diseases but are not required for cell growth or development. In contrast, Btype lamins have been considered essential in eukaryotic cells, with crucial roles in DNA replication and in the formation of the mitotic spindle. Knocking down the genes for B-type lamins (LMNB1, LMNB2) in HeLa cells has been reported to cause apoptosis. In the current study, we created conditional knockout alleles for mouse Lmnb1 and Lmnb2, with the goal of testing the hypothesis that B-type lamins are crucial for the growth and viability of mammalian cells in vivo. Using the keratin 14-Cre transgene, we bred mice lacking the expression of both Lmnb1 and Lmnb2 in skin keratinocytes (Lmnb1 D/D Lmnb2 D/D ). Lmnb1 and Lmnb2 transcripts were absent in keratinocytes of Lmnb1 D/D Lmnb2 D/D mice, and lamin B1 and lamin B2 proteins were undetectable. But despite an absence of B-type lamins in keratinocytes, the skin and hair of Lmnb1 D/D Lmnb2 D/D mice developed normally and were free of histological abnormalities, even in 2-year-old mice. After an intraperitoneal injection of bromodeoxyuridine (BrdU), similar numbers of BrdU-positive keratinocytes were observed in the skin of wild-type and Lmnb1 D/D Lmnb2 D/D mice. Lmnb1 D/D Lmnb2 D/D keratinocytes did not exhibit aneuploidy, and their growth rate was normal in culture. These studies challenge the concept that B-type lamins are essential for proliferation and vitality of eukaryotic cells.
Journal of Dermatological Science, 1998
To study the mechanism of basement membrane formation, we determined by immunochemistry temporal and spatial expression of laminin-5 (Ln-5), laminin-1 (Ln-1) and their integrin receptors during early skin morphogenesis. A 3dimensional skin culture was used that allows the study of the sequential molecular events of basement membrane formation at the epidermodermal interface. During early anchorage of keratinocytes to the extracellular matrix there is expression of Ln-5, BP-230 antigen and α3, β1 integrin subunits. During epidermal stratification and prior to the formation of the lamina densa there is assembly of Ln-5, Ln-1, collagen IV and nidogen accompanied by keratinocyte basal clustering of α2, α3, α6, β1, and β4 integrin subunits. The assembly pattern of Ln-1 and Ln-5 can be disturbed with functional antibodies against the β1 (AIIB2) and α6 (GoH3) integrin subunits. Ln-1 assembly can also be disturbed with antibodies against its E8 domain and by competitive inhibition with a synthetic peptide (AG-73) derived from its G-4 domain. Quantitative RT-PCR showed that the dermis contributes about 80% of the laminin γ1 chain mRNA while 20% is produced by the epidermis which emphasizes its dual tissue origin and the major contribution of the mesenchyma in laminin production. The laminin γ2 chain mRNA, present in Ln-5, was mostly of epidermal origin. This study presents evidence that during the initiation of basement membrane formation, laminins bind to keratinocyte plasma membrane receptors and thus may serve as nucleation sites for further polymerization of these compounds by a selfassembly process.
The FASEB Journal, 2001
Keratinocyte growth factor (KGF) is a paracrine mediator of epithelial cell growth. To examine the direct effects of KGF on the morphogenesis of the epidermis, we generated skin equivalents in vitro by seeding human keratinocytes on the papillary surface of acellular dermis and raising them up to the air-liquid interface. KGF was either added exogenously or expressed by keratinocytes via a recombinant retrovirus encoding KGF. KGF induced dramatic changes to the 3-dimensional organization of the epidermis including pronounced hyperthickening, crowding, and elongation of the basal cells, flattening of the rete ridges, and a ripple-like pattern in the junction of stratum corneum and granular layers. Quantitative immunostaining for the proliferation antigen, Ki67, revealed that in addition to increasing basal proliferation, KGF extended the proliferative compartment by inducing suprabasal cell proliferation. KGF also induced expression of the integrin alpha 5 beta 1 and delayed expression of keratin 10 and transglutaminase. However, barrier formation of the epidermis was not disrupted. These results demonstrate for the first time that a single growth factor can alter the 3-dimensional organization and proliferative function of an in vitro epidermis. In addition to new strategies for tissue engineering, such a well-defined system will be useful for analyzing growth factor effects on the complex links between cell proliferation, cell movement and differentiation within a stratified tissue.
Laminins of the dermo–epidermal junction
Matrix Biology, 1999
Laminins are the most abundant structural non-collagenous glycoproteins ubiquitously present in basement membranes. They are multidomain molecules constituting a family of possibly more than 50 members. Some members such as laminins 5, 6 and 10 are specific of the basal lamina present under stratified epithelia. Although only few intact laminin isoforms have been purified from cultivated cells or tissues, genetic engineering has opened the way for a rapid development of laminin structural biology. Moreover, the phenotypes resulting from gene targeting in mouse or from laminin defects in acquired or inherited human diseases highlight the pivotal role of laminins in morphogenesis, development, and physiology. Indeed, the laminins display a remarkable repertoire of functions, most importantly as structural elements forming a network throughout the basement membrane to which other collagenous or non-collagenous glycoproteins and proteoglycans attach. Furthermore, they are signaling molecules providing adjacent cells with diverse information by interacting with cell surface components. ᮊ
In skin, the distribution of integrins is compartmentalized. Whereas the aIJintegrin complex is polarized to the basal portion of proliferating cells in the basal layer juxtaposed to the basement membrane, ��3I�1 integrin receptors are localized on the cell surface surrounding basal and suprabasal cells, suggesting fi� integrins mediate both cell-matrix and cell-cell interactions. As initiation of maturation in skin is associated with the detachment of cells from the basement membrane, the early loss of aI3�, but not a3�1� integrin expression could be a determining factor in the transition from the proliferating to a differentiating keratinocyte. We have studied the regulation of adhesion potential and integrin expression during differentiation of mouse basal keratinocytes cultured in 0.05 m�.i Ca2 medium and induced to differentiate in 0.12 m�.i Ca2' medium. Within 12-24 h after elevation of Ca2�, a selective loss of the a6134 integrin complex is associated with the induction ...
Expression of the High-Affinity Laminin Receptor (67 kDa) in Normal Human Skin and Appendages
International Journal of Immunopathology and Pharmacology, 2005
The interaction of cells with extracellular matrix components plays a significant role in the regulation of cell biology. Laminin is a large glycoprotein involved in fundamental interactions between cells and the basement membrane. Several cell surface receptors are responsible for cell-matrix interactions. The 67 kDa high affinity laminin receptor, 67LR, is involved in the adhesion of normal cells to the laminin network and is also associated with the metastatic phenotype of some tumoral cells. We have investigated the expression of laminin and of the 67LR in normal human skin using immunoperoxidase staining. Twenty samples of skin were analyzed. Antibody against laminin reacted in a continuous linear band at the dermal-epidermal junction, as well as basement membranes of hair follicles, sebaceous and eccrine sweat glands, and dermal blood vessels. The epidermis and the follicular epithelium were negative for laminin. The 67LR seemed not to be expressed on the basal surface of basal keratinocytes. The major expression of this receptor may be detected in the upper half of the spinous layer and in the granular layer. The cells of the outer root sheath in hair follicle showed the same immunohistochemical pattern described for epidermis. In sebaceous glands and in eccrine sweat glands the secreting epithelium was positive. Endothelial cells of dermal blood vessels were routinely positive for 67LR. We observed that the expression of the 67LR in normal human skin is mostly located in epidermal areas in which the keratinizing process was particularly advanced.
Journal of Cell Biology, 2010
Fibroblast growth factors (FGFs) are master regulators of organogenesis and tissue homeostasis. In this study, we used different combinations of FGF receptor (FGFR)-deficient mice to unravel their functions in the skin. Loss of the IIIb splice variants of FGFR1 and FGFR2 in keratinocytes caused progressive loss of skin appendages, cutaneous inflammation, keratinocyte hyperproliferation, and acanthosis. We identified loss of FGF-induced expression of tight junction components with subsequent deficits in epidermal barrier function as the mechanism underlying the progressive inflammatory skin disease. The defective barrier causes activation of keratinocytes and epidermal γδ T cells, which produce interleukin-1 family member 8 and S100A8/A9 proteins. These cytokines initiate an inflammatory response and induce a double paracrine loop through production of keratinocyte mitogens by dermal cells. Our results identify essential roles for FGFs in the regulation of the epidermal barrier and i...
The EMBO journal, 1993
Keratinocyte growth factor (KGF) is a member of the fibroblast growth factor (FGF) family. Synthesized by cells of the dermal component of skin, KGF's potent mitogenic activity is on the epidermal component, which harbors the receptors for this factor. To explore the possible role of KGF in mesenchymal-epithelial interactions in skin, we used a human keratin 14 promoter to target expression of human KGF cDNA to the stratified squamous epithelia of transgenic mice. Mice expressing KGF in their epidermis typically appeared frail and weak, and often had grossly wrinkled skin. These mice exhibited a gross increase in epidermal thickness accompanied by alterations in epidermal growth and differentiation. Most remarkably, animals displayed several striking and unexpected changes, including a marked suppression of hair follicle morphogenesis and suppression of adipogenesis. With age, some animals developed gross transformations in the tongue epithelium and in epidermis. In addition, th...