Disease relevance of RABEPK

• Local intraocular production of p40 IL-12 thus prolonged corneal graft survival significantly, but local production of the prototypic immunomodulatory cytokine IL-4 induced eosinophilia, inflammation, and rejection [1].
• Our studies suggest that p40 may play a role in determining neuroblastoma phenotype by regulating MYCN and c-fos mRNA turnover [2].
• Serial measurement of the p40 titre in 12 patients with resected colorectal carcinoma shows a gradual return to normal with a half-life of 7 days [3].

High impact information on RABEPK

• Finally, p40 shows synergy with Rab9 in terms of its ability to stimulate mannose 6-phosphate receptor transport [4].
• The IL12B gene on chromosome 5q31-33 encodes the p40 subunit of interleukin 12, an immunomodulatory cytokine [5].
• The expression level of p40 was not affected in HeLa cell transformants cultured in 10% serum-supplemented media with the induction of antisense (AS)-p40 with 5 mM IPTG [6].
• Both the inhibition of cell growth and apoptotic cell death were partially rescued by the transfer of the p40 cDNA expression vector to AS-p40 clones [6].
• The induction of apoptosis in HeLa cells by the loss of LBP-p40 [6].

Biological context of RABEPK

• Based on the amino acid sequences of the proteins, we isolated two clones each of p40 and p50 from the ascidian hepatopancreas cDNA and determined the entire coding sequences of these clones [7].
• However, the small amount of local interleukin (IL)-12 p40 mRNA and the naïve phenotype of 20-50% of peritumoural T-lymphocytes are consistent with poor T-cell stimulation or erroneous recruitment [8].
• METHODS: We established a method to quantify p40/p46 and p69/p71 forms of 2-5AS mRNA by use of reverse transcription followed by competitive PCR [9].
• Although it has been demonstrated that transactivation of genes by gene products encoded by extra-chromosomal DNA may have nosocomial implications, whether transactivation by p40 tax generated from extra-chromosomal tax sequences is responsible for the development of neoplasia remains to be investigated [10].

Anatomical context of RABEPK

• Remarkably, similar analysis in a HEK293 cell line stably expressing dominant-negative kinase-deficient PIKfyveK1831E demonstrated a marked depletion of p40 from the HSP fraction [11].
• A band with the p40 electrophoretic mobility was found to react with a phosphoserine-specific antibody mainly in the PIKfyveWT-containing fractions obtained by density gradient sedimentation of total membranes from PIKfyveWT-expressing HEK293 cells [11].
• These data are consistent with a model in which p40 and Rab9 act together to drive the process of transport vesicle docking [4].
• In contrast, corneas expressing p40 IL-12 (n = 9) showed prolonged allograft survival (median day to rejection = 45 days, p = 0.003) [1].
• To elucidate the origin and evolution of ficolins, we separated approximately 40 kDa (p40) and approximately 50 kDa (p50) N-acetylglucosamine-binding lectins from hemolymph plasma of the solitary ascidian [7].

Associations of RABEPK with chemical compounds

• GST-p40 failed to specifically associate with the PIKfyve lipid products PtdIns 5-P and PtdIns 3,5-P2 in a liposome binding assay but was found to be an in vitro substrate of the PIKfyve serine kinase activity [11].
• Here we have evaluated plausible interaction of recombinant p40 with the PIKFyve products PtdIns 5-P and PtdIns 3,5-P2 by a synthetic-liposome binding assay [12].
• Binding assays revealed that p40 recognizes N-acetyl groups in association with a pyranose ring and that p50 recognizes N-acetylglucosamine alone [7].
• Quantitative analysis of p40/p46 and p69/p71 forms of 2',5'-oligoadenylate synthetase mRNA by competitive PCR and its clinical application [9].

Other interactions of RABEPK

• Active PIKfyve associates with and promotes the membrane attachment of the late endosome-to-trans-Golgi network transport factor Rab9 effector p40 [11].
• Differential centrifugation in a HEK293 cell line, stably expressing PIKfyveWT, showed the membrane-associated immunoreactive p40 co-sedimenting with PIKfyve in the high speed pellet (HSP) fraction [11].

Analytical, diagnostic and therapeutic context of RABEPK

• Here we report that p40, a Rab9 effector reported previously to bind Rab9-GTP and stimulate endosome-to-TGN transport, interacts with PIKfyve as determined by yeast two-hybrid assays, glutathione S-transferase (GST) pull-down assays, and co-immunoprecipitation in doubly transfected HEK293 cells [11].
• Stable transformants were isolated, and the expression of p40 was assayed by Western and Northern blotting [6].
• Quantitative analysis using dilution dot immunoblotting demonstrated a considerable increase in the titre of p40 in the sera of 51 patients with a wide range of advanced solid tumours when compared with 17 healthy controls and 50 patients with non-malignant diseases [3].
• All samples were analysed using immunohistochemistry with three different antibodies: 4A4 antibody recognising all p63 isoforms, p40 antibody reacting only with truncated dominant-negative isoforms (DeltaN-p63) and H-129 antibody recognising all alpha-isoforms [13].

References