Integrin-Linked Kinase Mediates Bone Morphogenetic Protein 7-Dependent Renal Epithelial Cell Morphogenesis

Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada
Molecular and Cellular Biology (Impact Factor: 4.78). 06/2005; 25(9):3648-57. DOI: 10.1128/MCB.25.9.3648-3657.2005
Source: PubMed


Bone morphogenetic protein 7 (BMP7) stimulates renal branching morphogenesis via p38 mitogen-activated protein kinase (p38MAPK) and activating transcription factor 2 (ATF-2) (M. C. Hu, D. Wasserman, S. Hartwig, and N. D. Rosenblum, J. Biol. Chem. 279:12051-12059, 2004). Here, we demonstrate a novel role for integrin-linked kinase (ILK) in mediating renal epithelial cell
morphogenesis in embryonic kidney explants and identify p38MAPK as a target of ILK signaling in a cell culture model of renal epithelial morphogenesis. The spatial and temporal expression
of ILK in embryonic mouse kidney cells suggested a role in branching morphogenesis. Adenovirus-mediated expression of ILK
stimulated and expression of a dominant negative ILK mutant inhibited ureteric bud branching in embryonic mouse kidney explants.
BMP7 increased ILK kinase activity in inner medullary collecting duct 3 (IMCD-3) cells, and adenovirus-mediated expression
of ILK increased IMCD-3 cell morphogenesis in a three-dimensional culture model. In contrast, treatment with a small molecule
ILK inhibitor or expression of a dominant negative-acting ILK (ILKE359K) inhibited epithelial cell morphogenesis. Further, expression of ILKE359K abrogated BMP7-dependent stimulation. To investigate the role of ILK in BMP7 signaling, we showed that ILK overexpression
increased basal and BMP7-induced levels of phospho-p38MAPK and phospho-ATF-2. Consistent with its inhibitory effects on IMCD-3 cell morphogenesis, expression of ILKE359K blocked BMP7-dependent increases in phospho-p38MAPK and phospho-ATF-2. Inhibition of p38MAPK activity with the specific inhibitor, SB203580, failed to inhibit BMP7-dependent stimulation of ILK activity, suggesting
that ILK functions upstream of p38MAPK during BMP7 signaling. We conclude that ILK functions in a BMP7/p38MAPK/ATF-2 signaling pathway and stimulates epithelial cell morphogenesis.

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Available from: Ming Chang Hu, Aug 06, 2014
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    • "Possible candidates include the PI3K/Akt and PI3K/RhoA pathways, that are known downstream targets of ILK and that have been implicated in reducing the potential for astrocytic differentiation [6]. However in other systems ILK signaling has also been linked to BMP and JAK-STAT signaling which are the major pathways involved in astrocytic differentiation [26], [51]. Delineation of the set of pathways that mediate the effects of ILK on astrogliosis will ultimately be required to design effective interventions for limiting gliosis after injury to the nervous system. "
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    ABSTRACT: Astrogliosis with glial scar formation after damage to the nervous system is a major impediment to axonal regeneration and functional recovery. The present study examined the role of β1-integrin signaling in regulating astrocytic differentiation of neural stem cells. In the adult spinal cord β1-integrin is expressed predominantly in the ependymal region where ependymal stem cells (ESCs) reside. β1-integrin signaling suppressed astrocytic differentiation of both cultured ESCs and subventricular zone (SVZ) progenitor cells. Conditional knockout of β1-integrin enhanced astrogliogenesis both by cultured ESCs and by SVZ progenitor cells. Previous studies have shown that injection into the injured spinal cord of a self-assembling peptide amphiphile that displays an IKVAV epitope (IKVAV-PA) limits glial scar formation and enhances functional recovery. Here we find that injection of IKVAV-PA induced high levels of β1-integrin in ESCs in vivo, and that conditional knockout of β1-integrin abolished the astroglial suppressive effects of IKVAV-PA in vitro. Injection into an injured spinal cord of PAs expressing two other epitopes known to interact with β1-integrin, a Tenascin C epitope and the fibronectin epitope RGD, improved functional recovery comparable to the effects of IKVAV-PA. Finally we found that the effects of β1-integrin signaling on astrogliosis are mediated by integrin linked kinase (ILK). These observations demonstrate an important role for β1-integrin/ILK signaling in regulating astrogliosis from ESCs and suggest ILK as a potential target for limiting glial scar formation after nervous system injury.
    Full-text · Article · Aug 2014 · PLoS ONE
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    • "In addition to its ability to mediate the phosphorylation of Akt and glycogen synthase kinase (GSK)3β [5], [6], [7], [22], ILK has been shown to serve as a scaffold protein linking integrins with the actin cytoskeleton [23], and to mediate growth factor/integrin-induced activation of ERKs [24], [25], [26], [27] or p38 [28], [29], [30], [31]. Equally important, ILK exhibits a unique ability to modulate the expression of growth factor receptors, including human epidermal growth factor receptor (HER)2 and epidermal growth factor receptor (EGFR), through the oncoprotein Y box-binding protein (YB)-1 [32], providing a link with growth factor receptor signaling. "
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    • "In these mice, detachment of the radial glia processes from the meningeal basal membrane was observed [41]. Integrin levels and/or signalling might therefore be compromised in the absence of Bmp7, since – for example – Bmp7 regulates, amongst others, the expression level of the integrin-linked kinase (ILK) encoding gene [49]. ILK is a major intracellular mediator of integrin-dependent basal lamina formation [50]. "
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    ABSTRACT: Bone morphogenetic proteins (BMPs) are considered important regulators of neural development. However, results mainly from a wide set of in vitro gain-of-function experiments are conflicting since these show that BMPs can act either as inhibitors or promoters of neurogenesis. Here, we report a specific and non-redundant role for BMP7 in cortical neurogenesis in vivo using knockout mice. Bmp7 is produced in regions adjacent to the developing cortex; the hem, meninges, and choroid plexus, and can be detected in the cerebrospinal fluid. Bmp7 deletion results in reduced cortical thickening, impaired neurogenesis, and loss of radial glia attachment to the meninges. Subsequent in vitro analyses of E14.5 cortical cells revealed that lack of Bmp7 affects neural progenitor cells, evidenced by their reduced proliferation, survival and self-renewal capacity. Addition of BMP7 was able to rescue these proliferation and survival defects. In addition, at the developmental stage E14.5 Bmp7 was also required to maintain Ngn2 expression in the subventricular zone. These data demonstrate a novel role for Bmp7 in the embryonic mouse cortex: Bmp7 nurtures radial glia cells and regulates fundamental properties of neural progenitor cells that subsequently affect Ngn2-dependent neurogenesis.
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