Ultraviolet B-Mediated Phosphorylation of the Small Heat Shock Protein HSP27 in Human Keratinocytes

Wong, Jon W.; Shi, Baojun; Farboud, Behnom; McClaren, Marla; Shibamoto, Takayuki; Cross, Carroll E.; Isseroff, Roslyn Rivkah

doi:10.1046/j.1523-1747.2000.00077.x

Cited by 44 publications

(53 citation statements)

References 49 publications

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“…41), and we suspect that these kinases are active developmentally and in adult epidermis. The p38 MAPK pathway resulting in HspB1 phosphorylation is active in keratinocytes subject to stress (31,42). In neither the Akt1 null or Akt2 null mouse is there complete dephosphorylation of HspB1 at Ser 86 (Fig.…”

Section: Discussionmentioning

confidence: 98%

“…Phosphorylation and redistribution of HspB1 from the cytoplasm to the nucleus after heat shock (30) and UVB exposure (29,31) has been demonstrated in cultured keratinocytes, with UVB-medi- ated cytoplasmic to nuclear shuttling downstream of p38 MAPK signaling (31). Hence, the stress-responsive phosphorylation of HspB1 and Akt-mediated phosphorylation produce opposite cellular localization effects.…”

Section: Discussionmentioning

confidence: 99%

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AKT-dependent HspB1 (Hsp27) Activity in Epidermal Differentiation

O'Shaughnessy

Welti

Cooke

et al. 2007

Journal of Biological Chemistry

117

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AKT activity has been reported in the epidermis associated with keratinocyte survival and differentiation. We show in developing skin that Akt activity associates first with post-proliferative, para-basal keratinocytes and later with terminally differentiated keratinocytes that are forming the fetal stratum corneum. In adult epidermis the dominant Akt activity is in these highly differentiated granular keratinocytes, involved in stratum corneum assembly. Stratum corneum is crucial for protective barrier activity, and its formation involves complex and poorly understood processes such as nuclear dissolution, keratin filament aggregation, and assembly of a multiprotein cell cornified envelope. A key protein in these processes is filaggrin. We show that one target of Akt in granular keratinocytes is HspB1 (heat shock protein 27). Loss of epidermal HspB1 caused hyperkeratinization and misprocessing of filaggrin. Akt-mediated HspB1 phosphorylation promotes a transient interaction with filaggrin and intracellular redistribution of HspB1. This is the first demonstration of a specific interaction between HspB1 and a stratum corneum protein and indicates that HspB1 has chaperone activity during stratum corneum formation. This work demonstrates a new role for Akt in epidermis.The epidermis is the primary environmental barrier, protecting from infection, allergens, and damage from UV radiation. The major constituent of this epidermal barrier is the terminally differentiated, anuclear keratinocyte. This structure is bounded by a cornified envelope, an elaborate, cross-linked protein structure covalently bound to hydrophobic lipid externally and aggregated keratin internally (1). Formation of this structure is poorly understood.The complexity of keratinocyte terminal differentiation and the importance of precisely timed and compartmentalized processing is illustrated by the maturation of the stratum corneum protein filaggrin. Filaggrin is synthesized as a high molecular mass precursor comprising multiple subunits that are sequentially processed and modified in temporally and spatially regulated steps by diverse proteases and enzymes to produce mature filaggrin subunits. Mature filaggrin is thought to be important in the aggregation and collapse of the keratin network leading to flattening of the keratinocyte and the destruction of the nucleus in granular layer (terminally differentiating) keratinocytes (2). Filaggrin is also incorporated into the cornified envelope (2). Premature or aberrant filaggrin processing can be catastrophic, leading to disruption of cornified envelope integrity and skin barrier function (3-5) and is far more damaging than reduced filaggrin levels that, in contrast, lead only to mild skin defects (6).Possible regulators of protein processing and trafficking during terminal differentiation are heat shock proteins (Hsps). 2Hsps have diverse roles as cellular chaperones, anti-apoptotic factors, stress-protective proteins, and cytoskeletal stabilizers (7,8). Human HspB1 (Hsp27) (9 -11) and the mouse HspB1...

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

AKT-dependent HspB1 (Hsp27) Activity in Epidermal Differentiation

O'Shaughnessy

Welti

Cooke

et al. 2007

Journal of Biological Chemistry

117

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“…Nuclear accumulation of Hsp27 is a common effect of cell stress and is seen in response to heat shock [9], ischemia/re-oxygenation [20], UV irradiation [27], toxin exposure and other stresses [19]. The present study was designed to establish mechanisms regulating entry and distribution of Hsp27 within the nuclear compartment.…”

Section: Discussionmentioning

confidence: 99%

“…The entry of Hsp27 into the nucleus of cells has been previously shown to correlate strongly with Hsp27 phosphorylation [9,26,27]. However, biochemical isolates of nuclear Hsp27 contain nonphosphorylated Hsp27 [26], leaving the regulatory state of Hsp27 at specific sites within the nucleus unresolved.…”

Section: Introductionmentioning

confidence: 99%

Recruitment of phosphorylated small heat shock protein Hsp27 to nuclear speckles without stress

Bryantsev

Chechenova

Shelden

2007

Experimental Cell Research

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During stress, the mammalian small heat shock protein Hsp27 enters cell nuclei. The present study examines the requirements for entry of Hsp27 into nuclei of normal rat kidney (NRK) renal epithelial cells, and for its interactions with specific nuclear structures. We find that phosphorylation of Hsp27 is necessary for the efficient entry into nuclei during heat shock but not sufficient for efficient nuclear entry under control conditions. We further report that Hsp27 is recruited to an RNAse sensitive fraction of SC35 positive nuclear speckles, but not other intranuclear structures, in response to heat shock. Intriguingly, Hsp27 phosphorylation, in the absence of stress, is sufficient for recruitment to speckles found in post-anaphase stage mitotic cells. Additionally, pseudophosphorylated Hsp27 fused to a nuclear localization peptide (NLS) is recruited to nuclear speckles in unstressed interphase cells, but wildtype and nonphosphorylatable Hsp27 NLS fusion proteins are not. The expression of NLS-Hsp27 mutants does not enhance colony forming abilities of cells subjected to severe heat shock, but does regulate nuclear speckle morphology. These data demonstrate that phosphorylation, but not stress, mediates Hsp27 recruitment to an RNAse soluble fraction of nuclear speckles and support a site-specific role for Hsp27 within the nucleus.

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“…In addition to the proapoptotic role of p38 MAPK, a growing body of evidence also indicates that activation of this kinase is cytoprotective and that the cytoprotective role of p38 MAPK is attributed to phosphorylation of HSP27 and subsequent reorganization of F-actin (2,20,22,52). Because phosphorylation of HSP27 dissipates molecular chaperon activity and renders cells susceptible to oxidative stress and apoptosis, the mechanism of cytoprotection conferred by phosphorylation of HSP27 should be different from that mediated by the unphosphorylated form of HSP27.…”

Section: Discussionmentioning

confidence: 99%

Role of F-actin organization in p38 MAP kinase-mediated apoptosis and necrosis in neonatal rat cardiomyocytes subjected to simulated ischemia and reoxygenation

Okada

Otani

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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. Role of F-actin organization in p38 MAP kinase-mediated apoptosis and necrosis in neonatal rat cardiomyocytes subjected to simulated ischemia and reoxygenation. Am J Physiol Heart Circ Physiol 289: H2310 -H2318, 2005. First published July 22, 2005 doi:10.1152/ajpheart.00462.2005.-Activation of p38 mitogen-activated protein (MAP) kinase (MAPK) has been implicated in the mechanism of cardiomyocyte (CMC) protection and injury. The p38 MAPK controversy may be related to differential effects of this kinase on apoptosis and necrosis. We have hypothesized that p38 MAPK-mediated F-actin reorganization promotes apoptotic cell death, whereas it protects from osmotic stress-induced necrotic cell death. Cultured neonatal rat CMCs were subjected to 2 h of simulated ischemia followed by reoxygenation. p38 MAPK activity measured by phosphorylation of MAP kinase-activated protein (MAPKAP) kinase 2 was increased during simulated ischemia and reoxygenation. This was associated with translocation of heat shock protein 27 (HSP27) from the cytosolic to the cytoskeletal fraction and F-actin reorganization. Cytochrome c release from mitochondria, caspase-3 activation, and DNA fragmentation were increased during reoxygenation. Robust lactate dehydrogenase (LDH) release was observed under hyposmotic (140 mosM) reoxygenation. The p38 MAPK inhibitor SB-203580 abrogated activation of p38 MAPK, translocation of HSP27, and F-actin reorganization and prevented cytochrome c release, caspase-3 activation, and DNA fragmentation. Conversely, SB-203580 enhanced LDH release during hyposmotic reoxygenation. The F-actin disrupting agent cytochalasin D inhibited F-actin reorganization and prevented cytochrome c release, caspase-3 activation, and DNA fragmentation, whereas it enhanced LDH release during hyposmotic reoxygenation. When CMCs were incubated under the isosmotic condition for the first 15 min of reoxygenation, SB-203580 and cytochalasin D increased ATP content of CMCs and prevented LDH release after the conversion to the hyposmotic condition. These results suggest that F-actin reorganization mediated by activation of p38 MAPK plays a differential role in apoptosis and protection against osmotic stress-induced necrosis during reoxygenation in neonatal rat CMCs; however, the sarcolemmal fragility caused by p38 MAPK inhibition can be reversed during temporary blockade of physical stress during reoxygenation. mitogen-activated protein kinase; osmotic stress; apoptotic and necrotic cell death P38 MITOGEN-ACTIVATED PROTEIN (MAP) kinase (MAPK) exerts a pleiotropic effect on cardiomyocytes (CMCs) during ischemia and reperfusion (1,39). It has been demonstrated that p38

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Ultraviolet B-Mediated Phosphorylation of the Small Heat Shock Protein HSP27 in Human Keratinocytes

Cited by 44 publications

References 49 publications

AKT-dependent HspB1 (Hsp27) Activity in Epidermal Differentiation

AKT-dependent HspB1 (Hsp27) Activity in Epidermal Differentiation

Recruitment of phosphorylated small heat shock protein Hsp27 to nuclear speckles without stress

Role of F-actin organization in p38 MAP kinase-mediated apoptosis and necrosis in neonatal rat cardiomyocytes subjected to simulated ischemia and reoxygenation

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