[PRAF2, an endoplasmic reticulum gatekeeper, controls the cell-surface export of the GABA(B) receptor in neurons]

Pharmacological chaperone-rescued cystic fibrosis CFTR-F508del mutant overcomes PRAF2-gated access to endoplasmic reticulum exit sites

The endoplasmic reticulum exit of some polytopic plasma membrane proteins (PMPs) is controlled by arginin-based retention motifs. PRAF2, a gatekeeper which recognizes these motifs, was shown to retain the GABA_B-receptor GB1 subunit in the ER. We report that PRAF2 can interact on a stoichiometric basis with both wild type and mutant F508del Cystic Fibrosis (CF) Transmembrane Conductance Regulator (CFTR), preventing the access of newly synthesized cargo to ER exit sites. Because of its lower abundance, compared to wild-type CFTR, CFTR-F508del recruitment into COPII vesicles is suppressed by the ER-resident PRAF2. We also demonstrate that some pharmacological chaperones that efficiently rescue CFTR-F508del loss of function in CF patients target CFTR-F508del retention by PRAF2 operating with various mechanisms. Our findings open new therapeutic perspectives for diseases caused by the impaired cell surface trafficking of mutant PMPs, which contain RXR-based retention motifs that might be recognized by PRAF2.

Grape Seed Proanthocyanidins (GSPs) Inhibit the Development of Cutaneous Squamous Cell Carcinoma by Regulating the hsa_circ_0070934/miR-136-5p/PRAF2 Axis

Background

Grape seed proanthocyanidins (GSPs) have been shown to inhibit the progression of many cancers, including cutaneous squamous cell carcinoma (CSCC). Circular RNA (circRNA) is a key regulator for cancer progression. However, it is unclear whether GSPs can mediate the progression of CSCC by regulating circRNA.

Methods

Quantitative real-time PCR was conducted to determine the expression of hsa_circ_0070934, microRNA (miR)-136-5p and prenylated Rab acceptor family 2 (PRAF2). MTT assay and colony formation assay were used to assess cell proliferation. Cell cycle process and apoptosis were detected by flow cytometry, and cell migration and invasion were measured by transwell assay. Western blot analysis was utilized to examine protein expression. In addition, dual-luciferase reporter assay and RIP assay were used to evaluate the interaction between miR-136-5p and hsa_circ_0070934 or PRAF2. Subcutaneous xenograft models were constructed to explore the function of GSPs on CSCC tumor growth in vivo.

Results

GSPs could reduce hsa_circ_0070934 expression and inhibit CSCC cell proliferation, cell cycle process, migration, invasion, while promote apoptosis. Overexpressed hsa_circ_0070934 could reverse the suppressive effect of GSPs on CSCC cell progression. MiR-136-5p could be sponged by hsa_circ_0070934, and its overexpression also abolished the positively regulation of hsa_circ_0070934 on the progression of GSPs-induced CSCC cells. PRAF2 was a target of miR-136-5p, and its expression could be decreased by GSPs and increased by hsa_circ_0070934. The inhibitory effect of miR-136-5p on CSCC cell progression could be reversed by PRAF2 overexpression. Additionally, GSPs also could inhibit CSCC tumor growth in vivo.

Conclusion

Our data showed that GSPs regulated the hsa_circ_0070934/miR-136-5p/PRAF2 axis to restrain CSCC progression.

PRAF2 expression indicates unfavorable clinical outcome in hepatocellular carcinoma

Introduction

Prenylated Rab acceptor 1 domain family member 2 (PRAF2), a novel oncogene, has been shown to be essential for the development of several human cancers; however, its role in hepatocellular carcinoma (HCC) remains unclear.

Materials and methods

PRAF2 mRNA and protein expressions were examined in fresh tissues by quantitative reverse transcription-polymerase chain reaction and Western blot, respectively, and in 518 paraffin-embedded HCC samples by immunohistochemistry. The correlation of PRAF2 expression and clinical outcomes was determined by the Student's t-test, Kaplan-Meier test, and multivariate Cox regression analysis. The role of PRAF2 in HCC was investigated by cell viability, colony formation, and migration assays in vitro and with a nude mouse model in vivo.

Results

In our study, the PRAF2 expression was noticeably increased in HCC tissues at both the mRNA and protein levels compared with that of the nontumorous tissues. Kaplan-Meier analysis indicated that high PRAF2 expression was correlated with worse overall survival in a cohort of 518 patients with HCC. The prognostic implication of PRAF2 was verified by stratified survival analysis. The multivariate Cox regression model revealed PRAF2 as an independent poor prognostic factor for overall survival (hazard ratio = 1.244, 95% CI: 1.039-1.498, P<0.017) in HCC. The in vitro data demonstrated that PRAF2 overexpression markedly enhanced cell viability, colony formation, and cell migration. Moreover, ectopic expression of PRAF2 promoted tumor growth and metastasis in vivo.

Conclusion

Collectively, we conclude that PRAF2 is increased in HCC and is a novel unfavorable biomarker for prognostic prediction for patients with HCC.