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In vivo cleaved CDCP1 promotes early tumor dissemination via complexing with activated ?1 integrin and induction of FAK/PI3K/Akt motility signaling.

ABSTRACT: Specific cleavage of the transmembrane molecule, CUB domain-containing protein-1 (CDCP1), by plasmin-like serine proteases induces outside-in signal transduction that facilitates early stages of spontaneous metastasis leading to tumor cell intravasation, namely cell escape from the primary tumor, stromal invasion and transendothelial migration. We identified active ?1 integrin as a biochemical and functional partner of the membrane-retained 70-kDa CDCP1 fragment, newly generated from its full-length 135-kDa precursor though proteolytic cleavage by serine proteases. Both in cell cultures and in live animals, active ?1 integrin complexed preferentially with functionally activated, phosphorylated 70-kDa CDCP1. Complexing of ?1 integrin the 70-kDa with CDCP1 fragment induced intracellular phosphorylation signaling, involving focal adhesion kinase-1 (FAK) and PI3 kinase (PI3K)-dependent Akt activation. Thus, inhibition of FAK/PI3K activities by specific inhibitors as well as short-hairpin RNA downregulation of ?1 integrin significantly reduced FAK/Akt phosphorylation under conditions where CDCP1 was processed by serine proteases, indicating that FAK/PI3K/Akt pathway operates downstream of cleaved CDCP1 complexed with ?1 integrin. Furthermore, this complex-dependent signaling correlated positively with high levels of tumor cell intravasation and dissemination. Correspondingly, abrogation in vivo of CDCP1 cleavage either by unique cleavage-blocking monoclonal antibody 10-D7 or by inhibition of proteolytic activity of plasmin-like serine proteases with aprotinin prevented ?1 integrin/CDCP1 complexing and downstream FAK/Akt signaling concomitant with significant reduction of stromal invasion and spontaneous metastasis. Therefore, ?1 integrin appears to serve as a motility-regulating partner mediating cross-talk between proteolytically cleaved, membrane-retained CDCP1 and members of FAK/PI3K/Akt pathway. This CDCP1 cleavage-induced signaling cascade constitutes a unique mechanism, independent of extracellular matrix remodeling, whereby a proteolytically cleaved CDCP1 regulates in vivo locomotion and metastasis of tumor cells through ?1 integrin partnering. Our findings indicate that CDCP1 cleavage, occurring at the apex of a ?1 integrin/FAK/PI3K/Akt signaling cascade, may represent a therapeutic target for CDCP1-positive cancers.

SUBMITTER: Casar B

PROVIDER: S-EPMC3931462 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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In vivo cleaved CDCP1 promotes early tumor dissemination via complexing with activated β1 integrin and induction of FAK/PI3K/Akt motility signaling.

Casar B B Rimann I I Kato H H Shattil S J SJ Quigley J P JP Deryugina E I EI

Oncogene 20121203 2

Specific cleavage of the transmembrane molecule, CUB domain-containing protein-1 (CDCP1), by plasmin-like serine proteases induces outside-in signal transduction that facilitates early stages of spontaneous metastasis leading to tumor cell intravasation, namely cell escape from the primary tumor, stromal invasion and transendothelial migration. We identified active β1 integrin as a biochemical and functional partner of the membrane-retained 70-kDa CDCP1 fragment, newly generated from its full-le ...[more]

PMID: 23208492

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Project description:Accumulating evidence suggests neuronal apoptosis has the potential to lead to more harmful effects in the pathological processes following traumatic brain injury (TBI). Previous studies have established that milk fat globule-EGF factor-8 (MFG-E8) provides neuroprotection through modulation of inflammation, oxidative stress, and especially apoptosis in cerebral ischemia and neurodegenerative disease. However, the effects of MFG-E8 on neuronal apoptosis in TBI have not yet been investigated. Therefore, we explored the role of MFG-E8 on anti-apoptosis and its potential mechanism following TBI. In the first set of experiments, adult male Sprague-Dawley (SD) rats were randomly divided into Sham and TBI groups that were each further divided into five groups representing different time points (6?h, 24?h, 72?h, and 7 days) (n?=?9 each). Western blotting, quantitative real-time PCR, and immunofluorescence staining were performed to identify the expression and cellular localization of MFG-E8. In the second set of experiments, four groups were randomly assigned: Sham group, TBI?+?Vehicle group, and TBI?+?rhMFG-E8 (1 and 3?µg) (n?=?15). Recombinant human MFGE8 (rhMFG-E8) was administrated as two concentrations through intracerebroventricular (i.c.v.) injection at 1?h after TBI induction. Brain water content, neurological severity score, western blotting, and immunofluorescence staining were measured at 24 and 72?h following TBI. In the final set of experiments, MFG-E8 siRNA (500?pmol/3?µl), integrin ?3 siRNA (500?pmol/3?µl), and PI3K inhibitor LY294002 (5 and 20?µM) were injected i.c.v. and thereafter rats exposed to TBI. Western blotting, immunofluorescence staining, brain water content, neurological severity score, and Fluoro-Jade C (FJC) staining were used to investigate the effect of the integrin-?3/FAK/PI3K/AKT signaling pathway on MFG-E8-mediated anti-apoptosis after TBI. The expression of MFG-E8 was mainly located in microglial cells and increased to peak at 24?h after TBI. Treatment with rhMFG-E8 (3?µg) markedly decreased brain water content, improved neurological deficits, and reduced neuronal apoptosis at 24 and 72?h after TBI. rhMFG-E8 significantly enhanced the expression of integrin-?3/FAK/PI3K/AKT pathway-related components. Administration of integrin-?3 siRNA and LY294002 (5 and 20?µM) abolished the effect of rhMFG-E8 on anti-apoptosis and neuroprotection after TBI. This study demonstrated for the first time that rhMFG-E8 inhibits neuronal apoptosis and offers neuroprotection. This is suggested to occur through the modulation of the integrin-?3/FAK/PI3K/AKT signaling pathway, highlighting rhMFG-E8 as a potentially promising therapeutic strategy for TBI patients.

Dataset Information

In vivo cleaved CDCP1 promotes early tumor dissemination via complexing with activated ?1 integrin and induction of FAK/PI3K/Akt motility signaling.

Publications

In vivo cleaved CDCP1 promotes early tumor dissemination via complexing with activated β1 integrin and induction of FAK/PI3K/Akt motility signaling.

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