Parstatin inhibits viability of human retinal pigment epithelium cells: an in vitro cytotoxicity study

OBJECTIVE

Parstatin, the N-terminal 41-amino-acid peptide cleaved by thrombin from protease-activated-receptor 1, was shown to be highly effective in preventing ocular angiogenesis and as such it has potential therapeutic applications in ocular neovascular diseases. In the frame of a safety program in preclinical development, we investigated whether parstatin exerts any cytotoxic effect in critical ocular cell populations.

MATERIALS AND METHODS

Human retinal pigment epithelium cell-19 line (ARPE-19) and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay were used to investigate parstatin's effect in cell cultures. Parstatin 24-41 was used as a control peptide which lacks the hydrophobic domain to demonstrate the specificity and the structure-dependent effect of parstatin. Both peptides were used at concentrations ranging from 0.1-30 μM for 24, 48 and 72 hours.

RESULTS

In the presence of parstatin the rate of ARPE-19 cell growth and viability were significantly decreased in a concentration-dependent and time-dependent manner, with an IC50 of approximately 10 μM. When ARPE-19 cells were treated with parstatin 24-41 no inhibitory effect was observed at any concentration or exposure time used.

CONCLUSIONS

Parstatin has a clear detrimental effect on the viability of ARPE-19 cells and raises concerns about its use in the eye because of its possible toxic effects.

Proteomic Analysis of Human Angiogenin Interactions Reveals Cytoplasmic PCNA as a Putative Binding Partner

Human Angiogenin (hAng) is a member of the ribonuclease A superfamily and a potent inducer of neovascularization. Protein interactions of hAng in the nucleus and cytoplasm of the human umbilical vein cell line EA.hy926 have been investigated by mass spectroscopy. Data are available via ProteomeXchange with identifiers PXD006583 and PXD006584. The first gel-free analysis of hAng immunoprecipitates revealed many statistically significant potential hAng-interacting proteins involved in crucial biological pathways. Surprisingly, proliferating cell nuclear antigen (PCNA), was found to be immunoprecipitated with hAng only in the cytoplasm. The hAng-PCNA interaction and colocalization in the specific cellular compartment was validated with immunoprecipitation, immunoblotting, and immunocytochemistry. The results revealed that PCNA is predominantly localized in the cytoplasm, while hAng is distributed both in the nucleus and in the cytoplasm. hAng and PCNA colocalize in the cytoplasm, suggesting that they may interact in this compartment.

Simian virus 40 large T antigen targets the spindle assembly checkpoint protein Bub1

The mitotic spindle checkpoint protein Bub1 has been found to be mutated at low frequency in certain human cancers characterized by aneuploidy. Simian virus 40 large T antigen efficiently immortalizes rodent cells and occasionally transforms them to tumorigenicity. T antigen can also cause genomic instability, inducing chromosomal aberrations and aneuploidy. Here, we report an interaction between Bub1 and T antigen. T antigen coimmunoprecipitates with endogenous Bub1 and Bub3, another component of the spindle checkpoint complex. Genetic analysis demonstrates that the interaction of T antigen with Bub1 is not required for immortalization but is closely correlated with transformation. T antigen induces an override of the spindle checkpoint dependent on Bub1 binding. This interaction with proteins of the spindle checkpoint machinery suggests another role for T antigen and provides insight into its ability to cause chromosomal aberrations, aneuploidy, and transformation.