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Autocrine transforming growth factor-{beta}1 activation mediated by integrin {alpha}V{beta}3 regulates transcriptional expression of laminin-332 in Madin-Darby canine kidney epithelial cells.

Moyano JV, Greciano PG, Buschmann MM, Koch M, Matlin KS - Mol. Biol. Cell (2010)

Bottom Line: Significantly, we show that expression of LM-332 in MDCK cells is an autocrine response to endogenous TGF-β1 secretion and activation mediated by integrin αVβ3 because neutralizing antibodies block LM-332 production in subconfluent cells.In confluent cells, latent TGF-β1 is secreted apically, whereas TβR-I and integrin αVβ3 are localized basolaterally.Disruption of the epithelial barrier by mechanical injury activates TGF-β1, leading to LM-332 expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Committee on Cell Physiology, and Committee on Molecular Pathogenesis and Molecular Medicine, The University of Chicago, Chicago, IL 60637, USA. jvmoyano@uchicago.edu

ABSTRACT
Laminin (LM)-332 is an extracellular matrix protein that plays a structural role in normal tissues and is also important in facilitating recovery of epithelia from injury. We have shown that expression of LM-332 is up-regulated during renal epithelial regeneration after ischemic injury, but the molecular signals that control expression are unknown. Here, we demonstrate that in Madin-Darby canine kidney (MDCK) epithelial cells LM-332 expression occurs only in subconfluent cultures and is turned-off after a polarized epithelium has formed. Addition of active transforming growth factor (TGF)-β1 to confluent MDCK monolayers is sufficient to induce transcription of the LM α3 gene and LM-332 protein expression via the TGF-β type I receptor (TβR-I) and the Smad2-Smad4 complex. Significantly, we show that expression of LM-332 in MDCK cells is an autocrine response to endogenous TGF-β1 secretion and activation mediated by integrin αVβ3 because neutralizing antibodies block LM-332 production in subconfluent cells. In confluent cells, latent TGF-β1 is secreted apically, whereas TβR-I and integrin αVβ3 are localized basolaterally. Disruption of the epithelial barrier by mechanical injury activates TGF-β1, leading to LM-332 expression. Together, our data suggest a novel mechanism for triggering the production of LM-332 after epithelial injury.

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Proposed model for the regulation of LM-332 expression by TGF-β1 and the epithelial barrier. Confluent (polarized) epithelial cells form an intact epithelium with differentiated apical and basolateral domains. Latent TGF-β1 is secreted apically but is separated from the activation machinery (composed at least by integrin αVβ3) and the TGF-β Receptor I (TβR-I) by intact epithelial junctional complexes. When the epithelium is wounded (cell–cell contacts disrupted), latent TGF-β1 is able to interact with integrin αVβ3 which activates it by an unidentified mechanism dependent on RGD [indicated by “? (RGD)”; see Discussion]. Activated TGF-β1 then binds to TβR-I, initiating transcription and expression of LM-332 and facilitating the restoration of a continuous epithelium (reepithelialization).
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Figure 9: Proposed model for the regulation of LM-332 expression by TGF-β1 and the epithelial barrier. Confluent (polarized) epithelial cells form an intact epithelium with differentiated apical and basolateral domains. Latent TGF-β1 is secreted apically but is separated from the activation machinery (composed at least by integrin αVβ3) and the TGF-β Receptor I (TβR-I) by intact epithelial junctional complexes. When the epithelium is wounded (cell–cell contacts disrupted), latent TGF-β1 is able to interact with integrin αVβ3 which activates it by an unidentified mechanism dependent on RGD [indicated by “? (RGD)”; see Discussion]. Activated TGF-β1 then binds to TβR-I, initiating transcription and expression of LM-332 and facilitating the restoration of a continuous epithelium (reepithelialization).

Mentions: In summary, our results describe a novel mechanism for regulation of LM-332 expression in epithelial cells (Figure 9). In it, renal epithelial cells, and possibly other epithelial cells, constitutively produce all of the components necessary to initiate LM-332 expression, including latent TGF-β, its receptors, and TGF-β activation machinery. When the cells are confluent and polarized, TGF-β can neither be activated nor signal because it is separated from the activation machinery and its receptors by the tight junctional barrier. When that barrier is breached, then TGF-β signaling ensues and LM-332 expression commences without delay. To our knowledge, this is only the second example of a signaling mechanism whose regulation is dependent in part on the integrity of an epithelial barrier (Vermeer et al., 2003), and the first such instance involving a component of the extracellular matrix. An implication of this proposed mechanism is that production of LM-332 is perhaps the most, proximal event after breakdown of the epithelial barrier. As such, it is conceivable that LM-332, acting through its receptors, helps to reprogram injured epithelial cells for restoration of epithelial continuity.


Autocrine transforming growth factor-{beta}1 activation mediated by integrin {alpha}V{beta}3 regulates transcriptional expression of laminin-332 in Madin-Darby canine kidney epithelial cells.

Moyano JV, Greciano PG, Buschmann MM, Koch M, Matlin KS - Mol. Biol. Cell (2010)

Proposed model for the regulation of LM-332 expression by TGF-β1 and the epithelial barrier. Confluent (polarized) epithelial cells form an intact epithelium with differentiated apical and basolateral domains. Latent TGF-β1 is secreted apically but is separated from the activation machinery (composed at least by integrin αVβ3) and the TGF-β Receptor I (TβR-I) by intact epithelial junctional complexes. When the epithelium is wounded (cell–cell contacts disrupted), latent TGF-β1 is able to interact with integrin αVβ3 which activates it by an unidentified mechanism dependent on RGD [indicated by “? (RGD)”; see Discussion]. Activated TGF-β1 then binds to TβR-I, initiating transcription and expression of LM-332 and facilitating the restoration of a continuous epithelium (reepithelialization).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2965683&req=5

Figure 9: Proposed model for the regulation of LM-332 expression by TGF-β1 and the epithelial barrier. Confluent (polarized) epithelial cells form an intact epithelium with differentiated apical and basolateral domains. Latent TGF-β1 is secreted apically but is separated from the activation machinery (composed at least by integrin αVβ3) and the TGF-β Receptor I (TβR-I) by intact epithelial junctional complexes. When the epithelium is wounded (cell–cell contacts disrupted), latent TGF-β1 is able to interact with integrin αVβ3 which activates it by an unidentified mechanism dependent on RGD [indicated by “? (RGD)”; see Discussion]. Activated TGF-β1 then binds to TβR-I, initiating transcription and expression of LM-332 and facilitating the restoration of a continuous epithelium (reepithelialization).
Mentions: In summary, our results describe a novel mechanism for regulation of LM-332 expression in epithelial cells (Figure 9). In it, renal epithelial cells, and possibly other epithelial cells, constitutively produce all of the components necessary to initiate LM-332 expression, including latent TGF-β, its receptors, and TGF-β activation machinery. When the cells are confluent and polarized, TGF-β can neither be activated nor signal because it is separated from the activation machinery and its receptors by the tight junctional barrier. When that barrier is breached, then TGF-β signaling ensues and LM-332 expression commences without delay. To our knowledge, this is only the second example of a signaling mechanism whose regulation is dependent in part on the integrity of an epithelial barrier (Vermeer et al., 2003), and the first such instance involving a component of the extracellular matrix. An implication of this proposed mechanism is that production of LM-332 is perhaps the most, proximal event after breakdown of the epithelial barrier. As such, it is conceivable that LM-332, acting through its receptors, helps to reprogram injured epithelial cells for restoration of epithelial continuity.

Bottom Line: Significantly, we show that expression of LM-332 in MDCK cells is an autocrine response to endogenous TGF-β1 secretion and activation mediated by integrin αVβ3 because neutralizing antibodies block LM-332 production in subconfluent cells.In confluent cells, latent TGF-β1 is secreted apically, whereas TβR-I and integrin αVβ3 are localized basolaterally.Disruption of the epithelial barrier by mechanical injury activates TGF-β1, leading to LM-332 expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Committee on Cell Physiology, and Committee on Molecular Pathogenesis and Molecular Medicine, The University of Chicago, Chicago, IL 60637, USA. jvmoyano@uchicago.edu

ABSTRACT
Laminin (LM)-332 is an extracellular matrix protein that plays a structural role in normal tissues and is also important in facilitating recovery of epithelia from injury. We have shown that expression of LM-332 is up-regulated during renal epithelial regeneration after ischemic injury, but the molecular signals that control expression are unknown. Here, we demonstrate that in Madin-Darby canine kidney (MDCK) epithelial cells LM-332 expression occurs only in subconfluent cultures and is turned-off after a polarized epithelium has formed. Addition of active transforming growth factor (TGF)-β1 to confluent MDCK monolayers is sufficient to induce transcription of the LM α3 gene and LM-332 protein expression via the TGF-β type I receptor (TβR-I) and the Smad2-Smad4 complex. Significantly, we show that expression of LM-332 in MDCK cells is an autocrine response to endogenous TGF-β1 secretion and activation mediated by integrin αVβ3 because neutralizing antibodies block LM-332 production in subconfluent cells. In confluent cells, latent TGF-β1 is secreted apically, whereas TβR-I and integrin αVβ3 are localized basolaterally. Disruption of the epithelial barrier by mechanical injury activates TGF-β1, leading to LM-332 expression. Together, our data suggest a novel mechanism for triggering the production of LM-332 after epithelial injury.

Show MeSH
Related in: MedlinePlus