Prediction of preeclampsia by placental protein 13 and background risk factors and its prevention by aspirin.

AIM: Evaluation of placental protein 13 (PP13) and risk factors (RFs) as markers for predicting preeclampsia (PE) and use of aspirin for PE prevention. MATERIALS AND METHODS: First-trimester pregnancy screening was based on having PP13 level ≤0.4 multiple of the median (MoM) and/or at least one major risk factor (RF) for PE. Management was by routine care or combined with daily treatment with 75 mg aspirin between 14 and 35 weeks of gestation. RESULTS: Of 820 deliveries, 63 women developed PE (7.7%). Median PP13 levels was 0.2MoM in the PE group compared with 0.83MoM among unaffected and 1.0MoM in unaffected not treated with aspirin (P<0.0001). Low PP13 was a better predictor for PE versus major RFs, particularly for young nuliparous. Combining low PP13 with RFs increased prediction accuracy. Mean arterial pressure (not included in the initial prediction), could add to prediction accuracy when combined with low PP13 and RFs. PE prevention by aspirin was most effective when the risk was determined by low PP13 alone, less effective for combining low PP13 with RFs, and ineffective when determined by RFs alone. CONCLUSION: When PE risk is determined by low first trimester PP13 or by combined low PP13 and RFs, prevention with aspirin is warranted.

First trimester maternal serum placental protein 13 levels in singleton vs. twin pregnancies with and without severe pre-eclampsia.

AIMS: To determine first trimester maternal serum placental protein 13 (PP13) in singletons vs. twins with and without severe preeclampsia (PE). METHODS: Serum samples were prospectively collected at 8-14 weeks of gestation. PP13 was determined by solid-phase immunoassay. Patients were recruited in community clinics throughout the country, and from the twin antenatal assessment clinic in Assaf Harofeh Medical Center, Zerifin, Israel. Demographics, medical, and pregnancy history were obtained at enrollment. Pregnancy outcome was collected after delivery. PP13 was compared by the Wilcoxon rank sum test. RESULTS: In singletons, PP13 declined with maternal weight and was lower in in vitro fertilization. Levels were converted into multiples of the median (MoMs) accordingly. In twins, the median was 1.74 MoM (n=76) vs. 1.00 in singletons (n=676, P<0.0001). Among twins with severe PE (n=10), the median was 1.53 MoM vs. 1.74 in unaffected twins (P=0.10), and 2.26 (n=6) for mild PE (P=0.30). Among singletons with severe PE, the median was 0.44 MoM (n=26, P<0.0001), and for mild PE 0.62 (n=17, P<0.001). CONCLUSION: PP13 is higher in twins than singletons, corresponding to the larger placental mass. Among singletons with severe PE, levels were significantly reduced, however, among twins, only a non-significant tendency for a reduction was recorded, and warrants further investigation in a larger series.

Participation of the proteasomal lid subunit Rpn11 in mitochondrial morphology and function is mapped to a distinct C-terminal domain.

Substrates destined for degradation by the 26 S proteasome are labelled with polyubiquitin chains. Rpn11/Mpr1, situated in the lid subcomplex, partakes in the processing of these chains or in their removal from substrates bound to the proteasome. Rpn11 also plays a role in maintaining mitochondrial integrity, tubular structure and proper function. The recent finding that Rpn11 participates in proteasome-associated deubiquitination focuses interest on the MPN+ (Mpr1, Pad1, N-terminal)/JAMM (JAB1/MPN/Mov34) metalloprotease site in its N-terminal domain. However, Rpn11 damaged at its C-terminus (the mpr1-1 mutant) causes pleiotropic effects, including proteasome instability and mitochondrial morphology defects, resulting in both proteolysis and respiratory malfunctions. We find that overexpression of WT (wild-type) RPN8, encoding a paralogous subunit that does not contain the catalytic MPN+ motif, corrects proteasome conformations and rescues cell cycle phenotypes, but is unable to correct defects in the mitochondrial tubular system or respiratory malfunctions associated with the mpr1-1 mutation. Transforming mpr1-1 with various RPN8-RPN11 chimaeras or with other rpn11 mutants reveals that a WT C-terminal region of Rpn11 is necessary, and more surprisingly sufficient, to rescue the mpr1-1 mitochondrial phenotype. Interestingly, single-site mutants in the catalytic MPN+ motif at the N-terminus of Rpn11 lead to reduced proteasome-dependent deubiquitination connected with proteolysis defects. Nevertheless, these rpn11 mutants suppress the mitochondrial phenotypes associated with mpr1-1 by intragene complementation. Together, these results point to a unique role for the C-terminal region of Rpn11 in mitochondrial maintenance that may be independent of its role in proteasome-associated deubiquitination.

The COP9 signalosome-like complex in S. cerevisiae and links to other PCI complexes.

The COP9 signalosome (CSN), the lid subcomplex of the proteasome and translational initiation factor 3 (eIF3) share structural similarities and are often referred to as the PCI family of complexes. In multicellular eukaryotes, the CSN is highly conserved as an 8-subunit complex but in Saccharomyces cerevisiae the complex is rather divergent. We further characterize the composition and properties of the CSN in budding yeast and its interactions with these related complexes. Using the generalized profile method we identified CSN candidates, four with PCI domains: Csn9, Csn10, Pci8/Csn11, and Csn12, and one with an MPN domain, Csn5/Rri1. These proteins and an additional interactor, Csi1, were tested for pairwise interactions by yeast two-hybrid and were found to form a cluster surrounding Csn12. Csn5 and Csn12 cofractionate in a complexed form with an apparent molecular weight of roughly 250kDa. However, Csn5 migrates as a monomer in Deltacsn12 supporting the pivotal role of Csn12 in stabilizing the complex. Confocal fluorescence microscopy detects GFP-tagged Csn5 preferentially in the nucleus, whereas in absence of Csn12, Csn10, Pci8/Csn11, or Csi1, Csn5 is delocalized throughout the cell, indicating that multiple subunits are required for nuclear localization of Csn5. Two CSN subunits, Csn9 and Csi1, interact with the proteasome lid subunit Rpn5. Pci8/Csn11 has previously been shown to interact with eIF3. Together, these results point to a network of interactions between these three structurally similar, yet functionally diverse, complexes.

MPN+, a putative catalytic motif found in a subset of MPN domain proteins from eukaryotes and prokaryotes, is critical for Rpn11 function.

BACKGROUND: Three macromolecular assemblages, the lid complex of the proteasome, the COP9-Signalosome (CSN) and the eIF3 complex, all consist of multiple proteins harboring MPN and PCI domains. Up to now, no specific function for any of these proteins has been defined, nor has the importance of these motifs been elucidated. In particular Rpn11, a lid subunit, serves as the paradigm for MPN-containing proteins as it is highly conserved and important for proteasome function. RESULTS: We have identified a sequence motif, termed the MPN+ motif, which is highly conserved in a subset of MPN domain proteins such as Rpn11 and Csn5/Jab1, but is not present outside of this subfamily. The MPN+ motif consists of five polar residues that resemble the active site residues of hydrolytic enzyme classes, particularly that of metalloproteases. By using site-directed mutagenesis, we show that the MPN+ residues are important for the function of Rpn11, while a highly conserved Cys residue outside of the MPN+ motif is not essential. Single amino acid substitutions in MPN+ residues all show similar phenotypes, including slow growth, sensitivity to temperature and amino acid analogs, and general proteasome-dependent proteolysis defects. CONCLUSIONS: The MPN+ motif is abundant in certain MPN-domain proteins, including newly identified proteins of eukaryotes, bacteria and archaea thought to act outside of the traditional large PCI/MPN complexes. The putative catalytic nature of the MPN+ motif makes it a good candidate for a pivotal enzymatic function, possibly a proteasome-associated deubiquitinating activity and a CSN-associated Nedd8/Rub1-removing activity.

COP9 signalosome components play a role in the mating pheromone response of S. cerevisiae.

A family of genetically and structurally homologous complexes, the proteasome lid, Cop9 signalosome (CSN) and eukaryotic translation initiation factor 3, mediate different regulatory pathways. The CSN functions in numerous eukaryotes as a regulator of development and signaling, yet until now no evidence for a complex has been found in Saccharomyces cerevisiae. We identified a group of proteins, including a homolog of Csn5/Jab1 and four uncharacterized PCI components, that interact in a manner suggesting they form a complex analogous to the CSN in S. cerevisiae. These newly identified subunits play a role in adaptation to pheromone signaling. Deletants for individual subunits enhance pheromone response and increase mating efficiency. Overexpression of individual subunits or a human homolog mitigates sst2-induced pheromone sensitivity. Csi1, a novel CSN interactor, exhibits opposite phenotypes. Deletants also accumulate Cdc53/cullin in a Rub1-modified form; however, this role of the CSN appears to be distinct from that in the mating pathway.