scholarly journals β1 Integrins Regulate Keratinocyte Adhesion and Differentiation by Distinct Mechanisms

2000 ◽  
Vol 11 (2) ◽  
pp. 453-466 ◽  
Author(s):  
Laurence Levy ◽  
Simon Broad ◽  
Dagmar Diekmann ◽  
Richard D. Evans ◽  
Fiona M. Watt
Keyword(s):  
Point Mutations ◽  
Terminal Differentiation ◽  
Focal Adhesions ◽  
Human Keratinocytes ◽  
Proximal Part ◽  
Epidermal Keratinocytes ◽  
Β1 Integrin ◽  
Primary Human Keratinocytes ◽  
Human Epidermal Keratinocytes ◽  
Β1 Integrins

In keratinocytes, the β1 integrins mediate adhesion to the extracellular matrix and also regulate the initiation of terminal differentiation. To explore the relationship between these functions, we stably infected primary human epidermal keratinocytes and an undifferentiated squamous cell carcinoma line, SCC4, with retroviruses encoding wild-type and mutant chick β1 integrin subunits. We examined the ability of adhesion-blocking chick β1-specific antibodies to inhibit suspension-induced terminal differentiation of primary human keratinocytes and the ability of the chick β1 subunit to promote spontaneous differentiation of SCC4. A D154A point mutant clustered in focal adhesions but was inactive in the differentiation assays, showing that differentiation regulation required a functional ligand-binding domain. The signal transduced by β1 integrins in normal keratinocytes was “do not differentiate” (transduced by ligand-occupied receptors) as opposed to “do differentiate” (transduced by unoccupied receptors), and the signal depended on the absolute number, rather than on the proportion, of occupied receptors. Single and double point mutations in cyto-2 and -3, the NPXY motifs, prevented focal adhesion targeting without inhibiting differentiation control. However, deletions in the proximal part of the cytoplasmic domain, affecting cyto-1, abolished the differentiation-regulatory ability of the β1 subunit. We conclude that distinct signaling pathways are involved in β1 integrin–mediated adhesion and differentiation control in keratinocytes.

Decreased expression of fibronectin and the alpha 5 beta 1 integrin during terminal differentiation of human keratinocytes

1991 ◽  
Vol 98 (2) ◽  
pp. 225-232 ◽  
Author(s):  
L.J. Nicholson ◽  
F.M. Watt
Keyword(s):  
Messenger Rna ◽  
Basal Layer ◽  
Terminal Differentiation ◽  
Human Keratinocytes ◽  
Epidermal Keratinocytes ◽  
Human Epidermal Keratinocytes ◽  
Fibronectin Receptor ◽  
Beta 1 Integrin ◽  
Differentiation Marker ◽  
Unit Gravity Sedimentation

We have examined the expression of fibronectin and the alpha 5 beta 1 fibronectin receptor during terminal differentiation of human epidermal keratinocytes, using involucrin as a terminal differentiation marker. The levels of mRNAs encoding fibronectin and the alpha 5 and beta 1 integrin subunits were measured in keratinocyte populations that had been enriched for involucrin-negative or -positive cells by unit gravity sedimentation or suspension-induced terminal differentiation. All three mRNAs decreased in abundance during terminal differentiation, and the corresponding proteins were localised by immunofluorescence to the basal layer in stratified colonies. We also examined expression in ndk, a strain of epidermal cells with a complete block in terminal differentiation, which, as a result, do not express involucrin. Messenger RNA levels for fibronectin and the alpha 5 and beta 1 subunits were higher in ndk, than in unfractionated keratinocytes and the corresponding proteins were expressed by all ndk, consistent with a basal keratinocyte phenotype. We conclude that expression of fibronectin and the alpha 5 beta 1 fibronectin receptor decreases during terminal differentiation and that such changes are likely to play a role in the selective migration of terminally differentiating cells from the basal epidermal layer.

scholarly journals Downregulation of 14-3-3σ Prevents Clonal Evolution and Leads to Immortalization of Primary Human Keratinocytes

2000 ◽  
Vol 149 (5) ◽  
pp. 1117-1130 ◽  
Author(s):  
Elena Dellambra ◽  
Osvaldo Golisano ◽  
Sergio Bondanza ◽  
Emanuela Siviero ◽  
Pedro Lacal ◽  
...  
Keyword(s):  
Replicative Senescence ◽  
Clonal Evolution ◽  
Human Keratinocytes ◽  
Telomerase Activity ◽  
Suppressor Gene ◽  
Epidermal Keratinocytes ◽  
Primary Human Keratinocytes ◽  
Human Epidermal Keratinocytes ◽  
Continuous Transition ◽  
Endogenous Gene

In human epidermal keratinocytes, replicative senescence, is determined by a progressive decline of clonogenic and dividing cells. Its timing is controlled by clonal evolution, that is, by the continuous transition from stem cells to transient amplifying cells. We now report that downregulation of 14-3-3σ, which is specifically expressed in human stratified epithelia, prevents keratinocyte clonal evolution, thereby forcing keratinocytes into the stem cell compartment. This allows primary human keratinocytes to readily escape replicative senescence. 14-3-3σ–dependent bypass of senescence is accompanied by maintenance of telomerase activity and by downregulation of the p16INK4a tumor suppressor gene, hallmarks of keratinocyte immortalization. Taken together, these data therefore suggest that inhibition of a single endogenous gene product fosters immortalization of primary human epithelial cells without the need of exogenous oncogenes and/or oncoviruses.

Alterations of ultrastructure and elemental composition in cultured human epidermal keratinocytes after treatment with nitrofurazone and silver sulfadiazine

1987 ◽  
Vol 45 ◽  
pp. 676-677
Author(s):  
A. R. Crooker ◽  
M. C. Myers ◽  
T. L. Beard ◽  
E. S. Graham
Keyword(s):  
Electron Microscopy ◽  
Elemental Composition ◽  
Pyrolytic Carbon ◽  
Human Keratinocytes ◽  
Silver Sulfadiazine ◽  
Epidermal Keratinocytes ◽  
Human Epidermal Keratinocytes ◽  
Culture Systems ◽  
Cytotoxicity Endpoints

Cell culture systems have become increasingly popular as a means of screening toxic agents and studying toxic mechanisms of drugs and other chemicals at the cellular and subcellular levels. These in vitro tests can be conducted rapidly in a broad range of relevant mammalian culture systems; a variety of biological and biochemical cytotoxicity endpoints can be examined. The following study utilized human keratinocytes to evaluate the relative cytotoxicities of nitrofurazone (NF) and silver sulfadiazine (SS), the active ingredients of FURACIN(R) Topical Cream and SILVADENE(R) Cream, respectively. These compounds are anti-infectives used in the treatment of burn patients. Cell ultrastructure and elemental composition were utilized as cytotoxicity endpoints.Normal Human Epidermal Keratinocytes (HK) were prepared from the EpiPackTM culture system (Clonetics Corporation, Boulder, CO). For scanning electron microscopy (SEM) and transmission electron microscopy (TEM), cells were seeded on sterile 35 mm Falcon plastic dishes; for elemental microanalysis, cells were plated on polished pyrolytic carbon discs (E. Fullam, Latham, NY) placed in the culture dishes.

scholarly journals Antioxidant and Pro-Oxidant Capacities as Mechanisms of Photoprotection of Olive Polyphenols on UVA-Damaged Human Keratinocytes

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2153
Author(s):  
Raffaella Marina Lecci ◽  
Isabella D’Antuono ◽  
Angela Cardinali ◽  
Antonella Garbetta ◽  
Vito Linsalata ◽  
...  
Keyword(s):  
Antioxidant Activities ◽  
Biological Activities ◽  
Human Keratinocytes ◽  
Ldl Oxidation ◽  
Trolox Equivalent Antioxidant Capacity ◽  
Epidermal Keratinocytes ◽  
Olive Cultivar ◽  
Human Epidermal Keratinocytes ◽  
Apoptotic Effect

A wide variety of polyphenols are reported to have considerable antioxidant and skin photoprotective effects, although the mechanisms of action are not fully known. Environmentally friendly and inexpensive sources of natural bioactive compounds, such as olive mill wastewater (OMWW), the by-product of olive-oil processing, can be considered an economic source of bioactive polyphenols, with a range of biological activities, useful as chemotherapeutic or cosmeceutical agents. Green strategies, such as the process based on membrane technologies, allow to recover active polyphenols from this complex matrix. This study aims to evaluate the antioxidant, pro-oxidant, and photoprotective effects, including the underlying action mechanism(s), of the ultra-filtered (UF) OMWW fractions, in order to substantiate their use as natural cosmeceutical ingredient. Six chemically characterized UF-OMWW fractions, from Italian and Greek olive cultivar processing, were investigated for their antioxidant activities, measured by Trolox Equivalent Antioxidant Capacity (TEAC), LDL oxidation inhibition, and ROS-quenching ability in UVA-irradiated HEKa (Human Epidermal Keratinocytes adult) cultures. The photoprotective properties of UF-OMWW were assayed as a pro-oxidant-mediated pro-apoptotic effect on the UVA-damaged HEKa cells, which can be potentially involved in the carcinogenesis process. All the UF-OMWW fractions exerted an effective antioxidant activity in vitro and in cells when administered together with UV-radiation on HEKa. A pro-oxidative and pro-apoptotic effect on the UVA-damaged HEKa cells were observed, suggesting some protective actions of polyphenol fraction on keratinocyte cell cultures.

Expression of a dominant negative cadherin mutant inhibits proliferation and stimulates terminal differentiation of human epidermal keratinocytes

1996 ◽  
Vol 109 (13) ◽  
pp. 3013-3023 ◽  
Author(s):  
A.J. Zhu ◽  
F.M. Watt
Keyword(s):  
Cell Adhesion ◽  
Terminal Differentiation ◽  
Intercellular Adhesion ◽  
Dominant Negative ◽  
Epidermal Keratinocytes ◽  
Dominant Negative Mutant ◽  
Beta Catenin ◽  
Human Epidermal Keratinocytes ◽  
Negative Mutant ◽  
E Cadherin

Cell adhesion molecules are not only required for maintenance of tissue integrity, but also regulate many aspects of cell behaviour, including growth and differentiation. While the regulatory functions of integrin extracellular matrix receptors in keratinocytes are well established, such functions have not been investigated for the primary receptors that mediate keratinocyte intercellular adhesion, the cadherins. To examine cadherin function in normal human epidermal keratinocytes we used a retroviral vector to introduce a dominant negative E-cadherin mutant, consisting of the extracellular domain of H-2Kd and the transmembrane and cytoplasmic domains of E-cadherin. As a control a vector containing the same construct, but with the catenin binding site destroyed, was prepared. High levels of expression of the constructs were achieved; the dominant negative mutant, but not the control, formed complexes with alpha-, beta- and gamma-catenin. In cells expressing the dominant negative mutant there was a 5-fold decrease in the level of endogenous cadherins and a 3-fold increase in the level of beta-catenin. Cell-cell adhesion and stratification were inhibited by the dominant negative mutant and desmosome formation was reduced. Expression of the mutant resulted in reduced levels of the alpha 2 beta 1 and alpha 3 beta 1 integrins and increased cell motility, providing further evidence for cross-talk between cadherins and the beta 1 integrins. In view of the widely documented loss of E-cadherin in keratinocyte tumours it was surprising that the dominant negative mutant had an inhibitory effect on keratinocyte proliferation and stimulated terminal differentiation even under conditions in which intercellular adhesion was prevented. These results establish a role for cadherins in regulating keratinocyte growth and differentiation and raise interesting questions as to the relative importance of cell adhesion-dependent and -independent mechanisms.

scholarly journals Envoplakin, a novel precursor of the cornified envelope that has homology to desmoplakin.

1996 ◽  
Vol 134 (3) ◽  
pp. 715-729 ◽  
Author(s):  
C Ruhrberg ◽  
M A Hajibagheri ◽  
M Simon ◽  
T P Dooley ◽  
F M Watt
Keyword(s):  
Plasma Membrane ◽  
Terminal Differentiation ◽  
Human Keratinocytes ◽  
Single Copy ◽  
Epidermal Keratinocytes ◽  
Single Copy Gene ◽  
Cornified Envelope ◽  
Keratin Filaments ◽  
Copy Gene

The cornified envelope is a layer of transglutaminase cross-linked protein that is deposited under the plasma membrane of keratinocytes in the outermost layers of the epidermis. We present the sequence of one of the cornified envelope precursors, a protein with an apparent molecular mass of 210 kD. The 210-kD protein is translated from a 6.5-kb mRNA that is transcribed from a single copy gene. The mRNA was upregulated during suspension-induced terminal differentiation of cultured human keratinocytes. Like other envelope precursors, the 210-kD protein became insoluble in SDS and beta-mercaptoethanol on activation of transglutaminases in cultured keratinocytes. The protein was expressed in keratinizing and nonkeratinizing stratified squamous epithelia, but not in simple epithelia or nonepithelial cells. Immunofluorescence staining showed that in epidermal keratinocytes, both in vivo and in culture, the protein was upregulated during terminal differentiation and partially colocalized with desmosomal proteins. Immunogold EM confirmed the colocalization of the 210-kD protein and desmoplakin at desmosomes and on keratin filaments throughout the differentiated layers of the epidermis. Sequence analysis showed that the 210-kD protein is homologous to the keratin-binding proteins desmoplakin, bullous pemphigoid antigen 1, and plectin. These data suggest that the 210-kD protein may link the cornified envelope to desmosomes and keratin filaments. We propose that the 210-kD protein be named "envoplakin."

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