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Ann-Marie Broome

Publications and source records attributed to Ann-Marie Broome.

9 recordsLinked to original sources
PubMed2005

Transglutaminase function in epidermis.

Surface epithelial cells, such as the epidermal keratinocyte, undergo a process of terminal cell differentiation that results in the construction of a multilayered epithelium. This epithelium functions to protect the organism from the environment. Transglutaminases, enzymes that catalyze the formation of isopeptide protein-protein cross-links, are key enzymes involved in the construction of this structure. This brief review will focus on the role of these enzymes in constructing the epidermal surface.

Epidermal Cells↗
PubMed2004

Microtubule-dependent redistribution of a cytoplasmic cornified envelope precursor.

Several cytoplasmic cornified envelope precursors have been described. Nevertheless, the mechanism whereby these proteins are positioned at the site of crosslink formation is not known. In this study, we examine the intracellular distribution of the cornified envelope precursor S100A11 (S100C) and the effects of the physiologic differentiating agent calcium on this distribution. S100A11 is localized in the cytoplasm of resting cultured human keratinocytes. Treatment with calcium causes S100A11 to relocate to the cell periphery. Immunoprecipitation studies reveal that S100A11 associates with microtubules, and inhibitor studies indicate that functional micro-tubules are required for S100A11 peripheral redistribution. Parallel studies indicate that S100A11 is not present in the Golgi or endoplasmic reticulum (ER), suggesting that S100A11 is not moved to the cell periphery via the classical Golgi/ER export pathway. Further evidence that the Golgi/ER is not involved is provided by the observation that the Golgi/ER disruptor brefeldin A does not alter movement. These results suggest that redistribution along microtubules is a mechanism whereby S100A11 is positioned at the cell periphery in preparation for transglutaminase-dependent crosslinking. Staining of epidermal tissue sections from uninvolved and psoriatic epidermis reveals strong staining at the cell periphery in the majority of suprabasal cells, confirming a peripheral distribution of S100A11 in vivo.

Antibody Specificity↗
PubMed2004

S100 proteins in the epidermis.

The S100 proteins comprise a family of 21 low molecular weight (9-13 kDa) proteins that are characterized by the presence of two calcium-binding EF-hand motifs. Fourteen S100 protein genes are located within the epidermal differentiation complex on human chromosome 1q21 and 13 S100 proteins (S100A2, S100A3, S100A4, S100A6, S100A7, S100A8, S100A9, S100A10, S100A11, S100A12, S100A15, S100B, and S100P) are expressed in normal and/or diseased epidermis. S100 proteins exist in cells as anti-parallel hetero- and homodimers and upon calcium binding interact with target proteins to regulate cell function. S100 proteins are of interest as mediators of calcium-associated signal transduction and undergo changes in subcellular distribution in response to extracellular stimuli. They also function as chemotactic agents and may play a role in the pathogenesis of epidermal disease, as selected S100 proteins are markedly overexpressed in psoriasis, wound healing, skin cancer, inflammation, cellular stress, and other epidermal states.

Epidermis↗
PubMed2004

Protein kinase Cdelta regulates keratinocyte death and survival by regulating activity and subcellular localization of a p38delta-extracellular signal-regulated kinase 1/2 complex.

Protein kinase Cdelta (PKCdelta) is an important regulator of apoptosis in epidermal keratinocytes. However, little information is available regarding the downstream kinases that mediate PKCdelta-dependent keratinocyte death. This study implicates p38delta mitogen-activated protein kinase (MAPK) as a downstream carrier of the PKCdelta-dependent death signal. We show that coexpression of PKCdelta with p38delta produces profound apoptosis-like morphological changes. These morphological changes are associated with increased sub-G(1) cell population, cytochrome c release, loss of mitochondrial membrane potential, caspase activation, and PARP cleavage. This death response is specific for the combination of PKCdelta and p38delta and is not produced by replacing PKCdelta with PKCalpha or p38delta with p38alpha. A constitutively active form of MEK6, an upstream activator of p38delta, can also produce cell death when coupled with p38delta. In addition, concurrent p38delta activation and extracellular signal-regulated kinase 1/2 (ERK1/2) inactivation are required for apoptosis. Regarding this inverse regulation, we describe a p38delta-ERK1/2 complex that may coordinate these changes in activity. We further show that this p38delta-ERK1/2 complex relocates into the nucleus in response to PKCdelta expression. This regulation appears to be physiological, since H(2)O(2), a known inducer of keratinocyte apoptosis, promotes identical PKCdelta and p38delta-ERK1/2 activity changes, leading to similar morphological changes.

Apoptosis↗
PubMed2003

A novel tumor suppressor protein promotes keratinocyte terminal differentiation via activation of type I transglutaminase.

Tazarotene-induced protein 3 (TIG3) is a recently discovered regulatory protein that is expressed in the suprabasal epidermis. In the present study, we show that TIG3 regulates keratinocyte viability and proliferation. TIG3-dependent reduction in keratinocyte viability is accompanied by a substantial increase in the number of sub-G1 cells, nuclear shrinkage, and increased formation of cornified envelope-like structures. TIG3 localizes to the membrane fraction, and TIG3-dependent differentiation is associated with increased type I transglutaminase activity. Microscopic localization and isopeptide cross-linking studies suggest that TIG3 and type I transglutaminase co-localize in membranes. Markers of apoptosis, including caspases and poly(ADP-ribose) polymerase, are not activated by TIG3, and caspase inhibitors do not stop the TIG3-dependent reduction in cell viability. Truncation of the carboxyl-terminal membrane-anchoring domain results in a complete loss of TIG3 activity. The morphology of the TIG3-positive cells and the effects on cornified envelope formation suggest that TIG3 is an activator of terminal keratinocyte differentiation. Our studies suggest that TIG3 facilitates the terminal stages in keratinocyte differentiation via activation of type I transglutaminase.

Adenoviridae↗
PubMed2003

A regulatory role for p38 delta MAPK in keratinocyte differentiation. Evidence for p38 delta-ERK1/2 complex formation.

p38 MAPK isoforms are important in the regulation of a variety of cellular processes. Among the four described p38 isoforms, p38 alpha, beta, and delta are expressed in keratinocytes (Dashti, S. R., Efimova, T., and Eckert, R. L. (2001) J. Biol. Chem. 276, 8059-8063). However, very little is known about how individual p38 isoforms regulate keratinocyte function. In the present study, we use okadaic acid (OA) as a tool to study the role of p38 MAPKs as regulators of keratinocyte differentiation. We demonstrate that OA activates p38 delta but not other p38 isoforms. p38 delta activation is increased as early as 0.5 h after OA addition, and activity is maximal at 8 and 24 h. ERK1 and ERK2 activity are reduced on an identical time course. We show that p38 delta forms a complex with ERK1/2, and overexpression of p38 delta inhibits ERK1/2 activity without reducing ERK1/2 level. Thus, p38 delta may directly suppress ERK1/2 activity. Additional studies show that p38 delta is expressed in the epidermis, suggesting a role for p38 delta in regulating differentiation. To evaluate its function, we show that increased p38 delta activity is associated with increased levels of AP1 and CAATT enhancer binding protein factors, increased binding of these factors to the involucrin (hINV) promoter, and increased expression. Moreover, these responses are maintained in the presence of SB203580, an agent that inhibits p38 alpha and beta, further suggesting a central role for the p38 delta isoform. Dominant-negative p38 also inhibits these responses. These unique observations suggest that p38 delta is the major p38 isoform driving suprabasal hINV gene expression and that p38 delta directly regulates ERK1/2 activity via formation of a p38 delta-ERK1/2 complex.

Adenoviridae↗
PubMed2003

S100A7 (psoriasin) interacts with epidermal fatty acid binding protein and localizes in focal adhesion-like structures in cultured keratinocytes.

S100 proteins are calcium-responsive signaling proteins that are overexpressed in cancer and inflammatory diseases. They act by forming complexes with target proteins to modify target protein function. Identifying S100 intracellular distribution, site of action, and protein targets are important goals. S100A7 (psoriasin) is an important member of this family that is markedly overexpressed in psoriatic keratinocytes; however, its role in disease progression is poorly understood. In this study, we express S100A7 in normal keratinocytes as a means to study S100A7 function. We show that S100A7 is present in the cytosol and in BiP/GRP78-positive (endoplasmic reticulum) tubular structures. When cells are challenged with elevated intracellular calcium, cytoplasmic S100A7 redistributes to alpha-actinin- and paxillin-positive peripheral structures that contact the substrate surface. Epidermal fatty acid binding protein is also overexpressed in psoriasis, and is a putative target of S100A7 in keratinocytes. To study this interaction, we coexpressed S100A7 and epidermal fatty acid binding protein. These studies indicate that S100A7 and epidermal fatty acid binding protein colocalize in the cytoplasm in untreated cultures, and localize in peripheral structures in response to calcium challenge. In addition, S100A7 expression appears to stabilize epidermal fatty acid binding protein level, and vice versa. Moreover, the proteins can be coprecipitated in the presence of bifunctional cross-linker, suggesting that they are part of a common complex. The colocalization with alpha-actinin and paxillin suggests that S100A7 and epidermal fatty acid binding protein colocalize in focal adhesion-like structures following calcium treatment.

Actinin↗
PubMed2003

S100 protein subcellular localization during epidermal differentiation and psoriasis.

S100 proteins are calcium-activated signaling proteins that interact with target proteins to modulate biological processes. Our present studies compare the level of expression, and cellular localization of S100A7, S100A8, S100A9, S100A10, and S100A11 in normal and psoriatic epidermis. S100A7 and S100A11 are present in the basal and spinous layers in normal epidermis. These proteins appear in the nucleus and cytoplasm in basal cells but are associated with the plasma membrane in spinous cells. S100A10 is present in basal and spinous cells, in the cytoplasm, and is associated with the plasma membrane. S100A8 and S100A9 are absent or are expressed at minimal levels in normal epidermis. In involved psoriatic tissue, S100A10 and S100A11 levels remain unchanged, whereas, S100A7, S100A8, and S100A9 are markedly overexpressed. The pattern of expression and subcellular localization of S100A7 is similar in normal and psoriatic tissue. S100A8 and S100A9 are strongly expressed in the basal and spinous layers in psoriasis-involved tissue. In addition, we demonstrate that S100A7, S100A10, and S100A11 are incorporated into detergent and reducing agent-resistant multimers, suggesting that they are in vivo transglutaminase substrates. S100A8 and S100A9 did not form these larger complexes. These results indicate that S100 proteins localize to the plasma membrane in differentiated keratinocytes, suggesting a role in regulating calcium-dependent, membrane-associated events. These studies also indicate, as reported previously, that S100A7, S100A8, and S100A9 expression is markedly altered in psoriasis, suggesting a role for these proteins in disease pathogenesis.

Annexin A2↗