Biomedical subjects

Lina Dagnino

Publications and source records attributed to Lina Dagnino.

4 recordsLinked to original sources

PubMed2003

Ca2+-dependent localization of integrin-linked kinase to cell junctions in differentiating keratinocytes.

Integrin complexes are necessary for proper proliferation and differentiation of epidermal keratinocytes. Differentiation of these cells is accompanied by down-regulation of integrins and focal adhesions as well as formation of intercellular adherens junctions through E-cadherin homodimerization. A central component of integrin adhesion complexes is integrin-linked kinase (ILK), which can induce loss of E-cadherin expression and epithelial-mesenchymal transformation when ectopically expressed in intestinal and mammary epithelia. In cultured primary mouse keratinocytes, we find that ILK protein levels are independent of integrin expression and signaling, since they remain constant during Ca(2+)-induced differentiation. In contrast, keratinocyte differentiation is accompanied by marked reduction in kinase activity in ILK immunoprecipitates and altered ILK subcellular distribution. Specifically, ILK distributes in close apposition to actin fibers along intercellular junctions in differentiated but not in undifferentiated keratinocytes. ILK localization to cell-cell borders occurs independently of integrin signaling and requires Ca(2+) as well as an intact actin cytoskeleton. Further, and in contrast to what is observed in other epithelial cells, ILK overexpression in differentiated keratinocytes does not promote E-cadherin down-regulation and epithelial-mesenchymal transition. Thus, novel tissue-specific mechanisms control the formation of ILK complexes associated with cell-cell junctions in differentiating murine epidermal keratinocytes.

Animals↗

PubMed2002

Active nuclear import and export pathways regulate E2F-5 subcellular localization.

Epidermal keratinocyte differentiation is accompanied by differential regulation of E2F genes, including up-regulation of E2F-5 and its concomitant association with the retinoblastoma family protein p130. This complex appears to play a role in irreversible withdrawal from the cell cycle in differentiating keratinocytes. We now report that keratinocyte differentiation is also accompanied by changes in E2F-5 subcellular localization, from the cytoplasm to the nucleus. To define the molecular determinants of E2F-5 nuclear import, we tested its ability to enter the nucleus in import assays in vitro using digitonin-permeabilized cells. We found that E2F-5 enters the nucleus through mediated transport processes that involve formation of nuclear pore complexes. It has been proposed that E2F-4 and E2F-5, which lack defined nuclear localization signal (NLS) consensus sequences, enter the nucleus in association with NLS-containing DP-2 or pRB family proteins. However, we show that nuclear import of E2F-5 only requires the first N-terminal 56 amino acid residues and is not dependent on interaction with DP or pRB family proteins. Because E2F-5 is predominantly cytoplasmic in undifferentiated keratinocytes and in other intact cells, we also examined whether this protein is subjected to active nuclear export. Indeed, E2F-5 is exported from the nucleus through leptomycin B-sensitive, CRM1-mediated transport, through a region corresponding to amino acid residues 130-154. This region excludes the DNA- and the p130-binding domains. Thus, the subcellular distribution of E2F-5 is tightly regulated in intact cells, through multiple functional domains that direct nucleocytoplasmic shuttling of this protein.

Active Transport, Cell Nucleus↗

PubMed2002

E2F-1 is essential for normal epidermal wound repair.

E2F factors are involved in proliferation and apoptosis. To understand the role of E2F-1 in the epidermis, we screened wild type and E2F-1(-/-) keratinocyte mRNA for genes differentially expressed in the two cell populations. We demonstrate the reduced expression of integrins alpha(5), alpha(6), beta(1), and beta(4) in E2F-1(-/-) keratinocytes associated with reduced activation of Jun terminal kinase and Erk upon integrin stimulation. As a consequence of altered integrin expression and function, E2F-1(-/-) keratinocytes also show impaired migration, adhesion to extracellular matrix proteins, and a blunted chemotactic response to transforming growth factor-gamma1. E2F-1(-/-) keratinocytes, but not dermal fibroblasts, exhibit altered patterns of proliferation, including significant delays in transit through both G(1) and S phases of the cell cycle. Recognizing that proliferation and migration are key for proper wound healing in vivo, we postulated that E2F-1(-/-) mice may exhibit abnormal epidermal repair upon injury. Consistent with our hypothesis, E2F-1(-/-) mice exhibited impaired cutaneous wound healing. This defect is associated with substantially reduced local inflammatory responses and rates of re-epithelialization. Thus, we demonstrate that E2F-1 is indispensable for a hitherto unidentified cell type-specific and unique role in keratinocyte proliferation, adhesion, and migration as well as in proper wound repair and epidermal regeneration in vivo.

Animals↗

PubMedDate not supplied

Delayed apoptosis post-cadmium injury in renal proximal tubule epithelial cells.

BACKGROUND: Accumulation of the widespread environmental toxin cadmium (Cd) in the kidney results initially in proximal tubule dysfunction. Exposure to Cd has been previously shown to induce apoptosis in LLC-PK (Lily Laboratory Culture, Porcine Kidney) cells, which are a model of proximal tubule epithelium. HYPOTHESIS: We postulated that modulation of the components of the apoptotic pathway triggered by Cd is amenable to therapeutic intervention. METHODS: We subjected confluent LLC-PK cells grown on two-compartment filters and on plastic to Cd (1-50 microM). Apoptosis and changes in components of the apoptotic pathway were measured by immunocytochemical and immunoblot analysis during the period of exposure and following Cd withdrawal. RESULTS: Insignificant apoptosis was seen during exposure to Cd and immediately after removal of this metal. Two waves of apoptosis were noted 6 and 48 h after the Cd was removed from the apical compartment. The apoptosis 48 h post-Cd exposure was accompanied by a decrease in cellular ATP levels and transepithelial resistance and preceded by an increase in p38 phosphorylation. Inhibition of p38 mitogen-activated protein kinase activity decreased the delayed apoptotic peak, without affecting the rate of recovery of the integrity of the renal epithelium. IGF-1 neither altered the delayed apoptosis nor facilitated the rate of recovery of the integrity of the renal epithelium. CONCLUSION: We demonstrate that following exposure to Cd, renal epithelial cells undergo significant apoptosis, which appears to involve p38 and is not amenable to IGF therapy.

Animals↗