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A novel extracellular Hsp90 mediated co-receptor function for LRP1 regulates EphA2 dependent glioblastoma cell invasion.

Gopal U, Bohonowych JE, Lema-Tome C, Liu A, Garrett-Mayer E, Wang B, Isaacs JS - PLoS ONE (2011)

Bottom Line: Hypoxia dramatically elevated surface expression of both eHsp90 and LRP1, concomitant with eHsp90 dependent activation of src, AKT, and EphA2.We herein demonstrate a novel crosstalk mechanism involving eHsp90-LRP1 dependent regulation of EphA2 function.We highlight a dual role for eHsp90 in transducing signaling via LRP1, and in facilitating LRP1 co-receptor function for EphA2.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina, United States of America.

ABSTRACT

Background: Extracellular Hsp90 protein (eHsp90) potentiates cancer cell motility and invasion through a poorly understood mechanism involving ligand mediated function with its cognate receptor LRP1. Glioblastoma multiforme (GBM) represents one of the most aggressive and lethal brain cancers. The receptor tyrosine kinase EphA2 is overexpressed in the majority of GBM specimens and is a critical mediator of GBM invasiveness through its AKT dependent activation of EphA2 at S897 (P-EphA2(S897)). We explored whether eHsp90 may confer invasive properties to GBM via regulation of EphA2 mediated signaling.

Principal findings: We find that eHsp90 signaling is essential for sustaining AKT activation, P-EphA2(S897), lamellipodia formation, and concomitant GBM cell motility and invasion. Furthermore, eHsp90 promotes the recruitment of LRP1 to EphA2 in an AKT dependent manner. A finding supported by biochemical methodology and the dual expression of LRP1 and P-EphA2(S897) in primary and recurrent GBM tumor specimens. Moreover, hypoxia mediated facilitation of GBM motility and invasion is dependent upon eHsp90-LRP1 signaling. Hypoxia dramatically elevated surface expression of both eHsp90 and LRP1, concomitant with eHsp90 dependent activation of src, AKT, and EphA2.

Significance: We herein demonstrate a novel crosstalk mechanism involving eHsp90-LRP1 dependent regulation of EphA2 function. We highlight a dual role for eHsp90 in transducing signaling via LRP1, and in facilitating LRP1 co-receptor function for EphA2. Taken together, our results demonstrate activation of the eHsp90-LRP1 signaling axis as an obligate step in the initiation and maintenance of AKT signaling and EphA2 activation, thereby implicating this pathway as an integral component contributing to the aggressive nature of GBM.

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Molecular crosstalk between eHSP90-LRP1 and AKT-EphA2 signaling.An eHSP90/LRP1 signaling axis is required to sustain src directed AKT activation, AKT dependent P-EphA2S897, and LRP1 recruitment to EphA2. These signaling events facilitate lamellipodia formation and support GBM cell motility and invasion. Hypoxia amplifies eHsp90 signaling and corresponding motility via enhanced LRP1 expression and Hsp90 secretion. NPGA inhibits eHsp90 signaling, with consequent inhibition of AKT, disruption of EphA2 and LRP1 complexes, and blockade of cell motility. ephrin A1 ligand similarly suppresses AKT activation, P-EphA2S897, EphA2-LRP1 complexes, and elicits comparable inhibitory effects upon GBM cell motility and invasion.
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pone-0017649-g006: Molecular crosstalk between eHSP90-LRP1 and AKT-EphA2 signaling.An eHSP90/LRP1 signaling axis is required to sustain src directed AKT activation, AKT dependent P-EphA2S897, and LRP1 recruitment to EphA2. These signaling events facilitate lamellipodia formation and support GBM cell motility and invasion. Hypoxia amplifies eHsp90 signaling and corresponding motility via enhanced LRP1 expression and Hsp90 secretion. NPGA inhibits eHsp90 signaling, with consequent inhibition of AKT, disruption of EphA2 and LRP1 complexes, and blockade of cell motility. ephrin A1 ligand similarly suppresses AKT activation, P-EphA2S897, EphA2-LRP1 complexes, and elicits comparable inhibitory effects upon GBM cell motility and invasion.

Mentions: Extracellular Hsp90 is emerging as a pivotal regulator of cell motility, invasion, and metastasis. Although the precise mechanisms of eHsp90 function remain largely unknown, eHsp90 regulates several well-established pro-motility molecules [19], [21], [23], [27]. Our current study linking eHsp90 signaling with EphA2-dependent cell motility and invasion adds a unique dimension to eHsp90's pro-tumorigenic repertoire. To our knowledge, this is the first report linking eHsp90-LRP1 signaling with EphA2 function. We show that eHsp90 promotes the recruitment of LRP1 to EphA2 in an AKT dependent manner and further demonstrate the previously unknown ability of LRP1 to exhibit specificity for a subset of AKT substrate proteins. Our data support a model whereby eHsp90-LRP1 dependent signaling is an obligate step for AKT activation and subsequent AKT directed phosphorylation of EphA2. This premise is supported by the shared ability of ephrin A1 ligand, NPGA or LRP1 silencing to suppress the phosphorylation of both AKT and EphA2, and to disrupt association between EphA2 and LRP1, culminating in the abrogation of lamellipodia formation and cell motility and invasion (Figure 6). Our studies therefore highlight a dual role for eHsp90 in transducing signaling via LRP1, while additionally promoting its LRP1 co-receptor functions to modulate EphA2 signaling, Recent reports highlighting the ability of eHsp90-LRP1 to elicit pro-motility function in normal and cancer cells [27], [42] portends a widespread role for this signaling pair in a variety of cancers that express EphA2. Whether eHsp90-LRP1 similarly regulates additional pro-motility receptors and intermediates is an area of active investigation.


A novel extracellular Hsp90 mediated co-receptor function for LRP1 regulates EphA2 dependent glioblastoma cell invasion.

Gopal U, Bohonowych JE, Lema-Tome C, Liu A, Garrett-Mayer E, Wang B, Isaacs JS - PLoS ONE (2011)

Molecular crosstalk between eHSP90-LRP1 and AKT-EphA2 signaling.An eHSP90/LRP1 signaling axis is required to sustain src directed AKT activation, AKT dependent P-EphA2S897, and LRP1 recruitment to EphA2. These signaling events facilitate lamellipodia formation and support GBM cell motility and invasion. Hypoxia amplifies eHsp90 signaling and corresponding motility via enhanced LRP1 expression and Hsp90 secretion. NPGA inhibits eHsp90 signaling, with consequent inhibition of AKT, disruption of EphA2 and LRP1 complexes, and blockade of cell motility. ephrin A1 ligand similarly suppresses AKT activation, P-EphA2S897, EphA2-LRP1 complexes, and elicits comparable inhibitory effects upon GBM cell motility and invasion.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3050925&req=5

pone-0017649-g006: Molecular crosstalk between eHSP90-LRP1 and AKT-EphA2 signaling.An eHSP90/LRP1 signaling axis is required to sustain src directed AKT activation, AKT dependent P-EphA2S897, and LRP1 recruitment to EphA2. These signaling events facilitate lamellipodia formation and support GBM cell motility and invasion. Hypoxia amplifies eHsp90 signaling and corresponding motility via enhanced LRP1 expression and Hsp90 secretion. NPGA inhibits eHsp90 signaling, with consequent inhibition of AKT, disruption of EphA2 and LRP1 complexes, and blockade of cell motility. ephrin A1 ligand similarly suppresses AKT activation, P-EphA2S897, EphA2-LRP1 complexes, and elicits comparable inhibitory effects upon GBM cell motility and invasion.
Mentions: Extracellular Hsp90 is emerging as a pivotal regulator of cell motility, invasion, and metastasis. Although the precise mechanisms of eHsp90 function remain largely unknown, eHsp90 regulates several well-established pro-motility molecules [19], [21], [23], [27]. Our current study linking eHsp90 signaling with EphA2-dependent cell motility and invasion adds a unique dimension to eHsp90's pro-tumorigenic repertoire. To our knowledge, this is the first report linking eHsp90-LRP1 signaling with EphA2 function. We show that eHsp90 promotes the recruitment of LRP1 to EphA2 in an AKT dependent manner and further demonstrate the previously unknown ability of LRP1 to exhibit specificity for a subset of AKT substrate proteins. Our data support a model whereby eHsp90-LRP1 dependent signaling is an obligate step for AKT activation and subsequent AKT directed phosphorylation of EphA2. This premise is supported by the shared ability of ephrin A1 ligand, NPGA or LRP1 silencing to suppress the phosphorylation of both AKT and EphA2, and to disrupt association between EphA2 and LRP1, culminating in the abrogation of lamellipodia formation and cell motility and invasion (Figure 6). Our studies therefore highlight a dual role for eHsp90 in transducing signaling via LRP1, while additionally promoting its LRP1 co-receptor functions to modulate EphA2 signaling, Recent reports highlighting the ability of eHsp90-LRP1 to elicit pro-motility function in normal and cancer cells [27], [42] portends a widespread role for this signaling pair in a variety of cancers that express EphA2. Whether eHsp90-LRP1 similarly regulates additional pro-motility receptors and intermediates is an area of active investigation.

Bottom Line: Hypoxia dramatically elevated surface expression of both eHsp90 and LRP1, concomitant with eHsp90 dependent activation of src, AKT, and EphA2.We herein demonstrate a novel crosstalk mechanism involving eHsp90-LRP1 dependent regulation of EphA2 function.We highlight a dual role for eHsp90 in transducing signaling via LRP1, and in facilitating LRP1 co-receptor function for EphA2.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina, United States of America.

ABSTRACT

Background: Extracellular Hsp90 protein (eHsp90) potentiates cancer cell motility and invasion through a poorly understood mechanism involving ligand mediated function with its cognate receptor LRP1. Glioblastoma multiforme (GBM) represents one of the most aggressive and lethal brain cancers. The receptor tyrosine kinase EphA2 is overexpressed in the majority of GBM specimens and is a critical mediator of GBM invasiveness through its AKT dependent activation of EphA2 at S897 (P-EphA2(S897)). We explored whether eHsp90 may confer invasive properties to GBM via regulation of EphA2 mediated signaling.

Principal findings: We find that eHsp90 signaling is essential for sustaining AKT activation, P-EphA2(S897), lamellipodia formation, and concomitant GBM cell motility and invasion. Furthermore, eHsp90 promotes the recruitment of LRP1 to EphA2 in an AKT dependent manner. A finding supported by biochemical methodology and the dual expression of LRP1 and P-EphA2(S897) in primary and recurrent GBM tumor specimens. Moreover, hypoxia mediated facilitation of GBM motility and invasion is dependent upon eHsp90-LRP1 signaling. Hypoxia dramatically elevated surface expression of both eHsp90 and LRP1, concomitant with eHsp90 dependent activation of src, AKT, and EphA2.

Significance: We herein demonstrate a novel crosstalk mechanism involving eHsp90-LRP1 dependent regulation of EphA2 function. We highlight a dual role for eHsp90 in transducing signaling via LRP1, and in facilitating LRP1 co-receptor function for EphA2. Taken together, our results demonstrate activation of the eHsp90-LRP1 signaling axis as an obligate step in the initiation and maintenance of AKT signaling and EphA2 activation, thereby implicating this pathway as an integral component contributing to the aggressive nature of GBM.

Show MeSH
Related in: MedlinePlus