Dynamic changes in the expression of DEP‐1 and other PDGF receptor‐antagonizing PTPs during onset and termination of neointima formation

Abstract

Growth factor-dependent tissue remodeling, such as restenosis, is believed to be predominantly regulated by changes in expression of receptor-tyrosine-kinases (RTKs) and their ligands. As endogenous antagonists of RTKs, protein-tyrosine-phosphatases (PTPs) are additional candidate regulators of these processes. Using laser-capture-microdissection and quantitative RT-polymerase chain reaction (qRT-PCR), we investigated the layer-specific expression of the four platelet-derived growth factor (PDGF) isoforms, the PDGF-alpha and beta receptors, and five PTPs implied in control of PDGF-receptor signaling 8 and 14 days after balloon injury of the rat carotid. Results were correlated with analyses of PDGF-beta receptor phosphorylation and vascular smooth muscle cell (VSMC) proliferation in vivo. The expression levels of all components, as well as receptor activation and VSMC proliferation, showed specific changes, which varied between media and neointima. Interestingly, PTP expression--particularly, DEP-1 levels--appeared to be the dominating factor determining receptor-phosphorylation and VSMC proliferation. In support of these findings, cultured DEP-1(-/-) cells displayed increased PDGF-dependent cell signaling. Hyperactivation of PDGF-induced signaling was also observed after siRNA-down-regulation of DEP-1 in VSMCs. The results indicate a previously unrecognized role of PDGF-receptor-targeting PTPs in controlling neointima formation. In more general terms, the observations indicate transcriptional regulation of PTPs as an important mechanism for controlling onset and termination of RTK-dependent tissue remodeling.

Density enhanced phosphatase-1 down-regulates urokinase receptor surface expression in confluent endothelial cells

“…Consistently, DEP-1 is shown to be important for contact inhibition of VEGFinduced proliferation 13 and during neo-intima formation. 42 That DEP-1 affects cell behavior has been shown for many cell types. 13,[43][44][45][46] For primary ECs, we here report that DEP-1 inhibited transmigration ( Figure 6A), proliferation ( Figure 6B), and formation of capillary-like structures ( Figure 6C).…”

12/15-lipoxygenase–derived lipid peroxides control receptor tyrosine kinase signaling through oxidation of protein tyrosine phosphatases

“…PDGF β-receptor phosphorylation and signaling is strongly influenced by multiple PTPs, including TC-PTP, PTP-1B, and DEP-1 (4,(34)(35)(36). We therefore investigated whether the increase in PTP oxidation in the Gpx4 −/− cells was associated with changes in PDGF β-receptor phosphorylation.…”

Chronic insulin treatment suppresses PTP1B function, induces increased PDGF signaling, and amplifies neointima formation in the balloon-injured rat artery

“…mRNA was reverse transcribed into cDNA with the use of a Transcriptor First Strand cDNA Synthesis kit from Roche (Indianapolis, IN) followed by the performance of real-time PCR for PTP1B using a LC 480 Real-Time PCR instrument (Roche Diagnostics). Results were normalized against cyclophilin or hypoxanthineguanine phosphoribosyl transferase (HGPRT) mRNA, because the expression of these housekeeping genes has been shown to remain stable in a rat carotid artery injury model (16,29). Real-time PCR was performed using the following probes derived from Universal probe library software (universalprobelibrary.com; Roche Applied Science): PTP1B primer, forward 5Ј-GGAACAGGTACCGAGATGTCA-3Ј and reverse 5Ј-AGTCATTATCTTCCTGATGCAATT-3Ј; cyclophilin primer, forward 5Ј-ACCTTCCACAGGGTCATCC-3Ј and reverse 5Ј-ACCTTCCACAGGGTCATCC-3Ј; and HGPRT primer, forward 5Ј-GTCAACGGGGGACATAAAG-3Ј and reverse 5Ј-TGCATTGT-TTTACCAGTGTCAA-3Ј.…”