Browsing by Subject "Keratinocytes"
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- PublicationOpen AccessAkt pathway as a target for therapeutic intervention in HNSCC(Murcia : F. Hernández, 2008) Moral, Marta; Paramio, Jesús M.Head and neck squamous cell carcinoma (HNSCC) is the sixth most common form of cancer worldwide. One frequent alteration found in this type of cancer is overactivation of the PI3K/PTEN/mTOR pathway, of which protein kinase B (PKB)/Akt is a central key element, controlling important cellular processes such as metabolism, cell size, proliferation and apoptosis, ultimately regulating cell growth and survival. Thus, drugs that target Akt directly or elements of the pathway are plausible candidates for cancer treatment. Accordingly, numerous clinical trials in various phases are being performed for these drugs. In this review, we discuss the tumorigenic capacity of Akt and focus on its role in HNSCC, paying special attention to the current efforts in treating this cancer in a more specific, Akttargeted way, based on its primordial role in this type of cancer.
- PublicationOpen AccessCharacterization of organotypic keratinocyte cultures on de-epithelialized bovine tongue mucosa(Murcia : F. Hernández, 2002) Hildebrand, H.C.; Häkkinen, L.; Wiebe, C.B.; Larjava, H.S.Organotypic cultures have been used to study epithelial cell behavior for many years. The aim of this study was to develop an organotypic culture method that better mimics the three-dimensional morphology of interdigitating rete ridges and connective tissue papillae and that also conserves the basement membrane zone (BMZ). Bovine tongue mucosa connective tissue, separated from epithelium after 1M NaCl incubation, was used as o rganotypic culture substratum for different human keratinocyte cell lines. Organotypic cultures were characterized by electron and immunofluorescence microscopy for expression of integrin subunits and extracellular matrix components. While spontaneously immortalized mucosal keratinocytes produced highly irregular stratified organotypic cultures, the normal human epidermal keratinocytes (NHEK) demonstrated culture morphology that resembled in vivo epidermis. However, in this model, the histomorphology, expression of differentiation markers involucrin, keratin 10 and 14, and integrins varied significantly between the cell lines. Some cultures appeared to have an extended survival since they were maintained up to 40 days without histological signs of degeneration. The ultrastructure of the BMZ including hemidesmosomes was similar to the normal dermo-epidermal junction. Extracellular matrix molecules, including tenascin, laminin-1 and -5, were expressed in the cultures demonstrating their secretion solely by keratinocytes. Distribution and expression of integrins in NHEK cultures was similar to that seen in vivo skin with the exception of additional expression of a5ß1 and avß6 integrins. Organotypic NHEK cultures show similarities to normal stratified epithelium and are potentially useful for multiple applications for studies on epithelial cell behavior in vitro.
- PublicationOpen AccessLessons from disorders of epidermal differentiation-associated keratins(Murcia : F. Hernández, 2002) Ishida-Yamamoto, A.; Takahashi, H.; lizuka, H.A number of diseases have been associated with mutations in genes encoding keratin intermediate filaments. Several of these disorders have skin manifestations, in which histological changes highlight the role of various different keratins in epidermal d i fferentiation. For example, mutations in either K1 or K10 (the major keratin pair expressed in diff e r e n t i a t e d keratinocytes) usually lead to clumped keratin filaments and cytolysis. Furthermore, the precise nature of the mutation has direct implications for disease phenotype. S p e c i f i c a l l y, mutations in the H1 and alpha-helical rod domains of K1/K10 result in bullous congenital ichthyosiform erythroderma, underscoring the critical role for this keratin filament domain in maintaining cellular integrity. However, a lysine to isoleucine substitution in the V1 domain of K1 underlies a form of palmoplantar keratoderma, which has different cell biological implications. Keratins are cross-linked into the cornified cell envelopes through this particular lysine residue and the consequences of the mutation lead to changes in keratin-desmosome association and cornified cell morphology, suggesting a role for this keratin subdomain in cornified cell envelope formation. Recently, to extend genotype-phenotype correlation, a frameshift mutation in the V2 region of the K1 tail domain was identified in ichthyosis hystrix (Curth-Macklin type), in which keratin filaments show a characteristic shell-like structure and fail to form proper bundles. In this case, the association of desmosomes with loricrin was also altered, implicating this keratin domain in organizing the intracellular distribution of loricrin during cornification. C o l l e c t i v e l y, these mutations in K1/K10 provide a fascinating insight into both normal and abnormal processes of epidermal differentiation.
- PublicationOpen AccessLoricrin and human skin diseases: molecular basis of loricrin keratodermas(Murcia : F. Hernández, 1998) Ishida-Yamamoto, A.; Takahashi, H.; lizuka, H.The cornified cell envelope (CE) is a tough structure formed beneath the plasma membrane of terminally differentiated keratinocytes. Recent progress in understanding the molecular organization of the CE has disclosed the complex, yet orderly structure that functions as a protective barrier against the environment. We have recently demonstrated that two inherited skin diseases, Vohwinkel's syndrome (VS) and progressive symmetric erythrokeratoderma (PSEK) may result from mutations in the gene encoding loricrin, a major constituent of the CE. In adult human epidermis, loricrin is diffusely distributed within the superficial granular cells. In the cornified cells, loricrin is associated with CEs. In some patients with VS and PSEK skin, however, granular cells contain many intranuclear granules which are labeled with an amino-terminal loricrin antibody. CEs are thinner than normal and sparsely labeled with the loricrin antibody. Parakeratotic cornified cells contain loricrin-positive granules. Sequencing of the loricrin gene has disclosed heterozygous mutations; insertion of one nucleotide (730insG, 709insC) that shifts the reading frame in these patients. Consequently the carboxyl-terminus are replaced by highly charged missense sequences that override the endogeneous termination codon extending the protein with an additional 22 amino acids. Elucidation of the molecular biology of "loricrin keratodermas" adds to our understanding of the complexity and biological significance of the CE.
- PublicationOpen AccessMechanisms of human skin cell motility(Murcia : F. Hernández, 2004) Li, W.; Fan, J.; Chen, M.; Woodley, D.T.The extracellular matrix (ECM) in contact with the cells and the soluble growth factors (GFs) binding to their cell surface receptors are the two main signals that directly regulate cell motility. Human keratinocytes and dermal fibroblasts are two primary cell types in skin that must undergo migration for skin wounds to heal. In this cell migration, ECMs play an “active” role by providing the cells with both focal adhesions and a migration-initiating signal, even in the absence of GFs. In contrast, GFs cannot initiate cell migration in the absence of a pro-migratory ECM. Rather, GFs play a “passive” role by enhancing the ECM-initiated motility and giving the moving cells directionality. Inside the cells, the initiation signal of the ECM and the optimization signals of the GFs are propagated by both overlapping and discrete signaling networks. However, activation of no single signaling pathway by itself is sufficient to replace the role of ECMs or GFs. This review focuses on our current understanding of both the individual and the combined functions of ECMs and GFs in the control of skin cell motility. An abbreviation of the terminologies used in this article is provided.
- PublicationOpen AccessRho GTPases and Nox dependent ROS production in skin. Is there a connection?(F. Hernández y Juan F. Madrid. Universidad de Murcia. Departamento de Biología Celular e Histología, 2012) Stanley, Alanna; Hynes, Ailish; Brakebusch, Cord; Quondamatteo, FabioRho GTPases are a family of small GTP binding proteins most commonly known for the regulation of many cellular processes, including actin cytoskeleton re-organisation, cell proliferation, signal transduction and regulation of apoptosis. Additionally, a link between Rho GTPases and reactive oxygen species (ROS) has been shown. In line with the growing interest in the role of ROS in cell biology, the relevance of this connection is becoming increasingly clearer. ROS production is classically associated with oxidative metabolic pathways (e.g. respiratory chain, arachidonic acid). During these metabolic pathways, ROS are produced as by-products and these can be potentially toxic. However, numerous cell types contain dedicated enzymatic complexes, i.e., NADPH oxidase (Nox) complexes, for regulated production of ROS. This regulated production of ROS seems to be important for a number of fundamental cell biological processes, including cell growth, differentiation, migration, angiogenesis, aimed at maintaining tissue homeostasis. Data suggests that skin cells are capable of a regulated ROS production via Nox complexes. Members of the Rho GTPase family have been found to play a central regulatory role in Nox activity. In the present review we will focus on the involvement of Rho GTPases in regulated production of ROS with special emphasis on the skin. We will also discuss the possibility that some in vivo effects of the deletion of members of the Rho GTPase family in skin cells could potentially be linked to a reduced ability of regulated ROS production.