Modifications of low-density lipoprotein induced by arterial proteoglycans and chondroitin-6-sulfate

Association of low-density lipoproteins (LDL) with arterial chondroitin sulfate proteoglycans (CSPG) appears to contribute to their deposition in the extracellular intimal compartment and to its internalization by macrophages. CSPG and LDL interact by ionic bridges with formation of soluble and insoluble complexes. We studied the alterations on LDL structure induced by its association with arterial CSPG and other glycosaminoglycans (GAG). In soluble complexes, at low and physiological ionic strength, arterial CSPG and sulfated GAG modify the kinetics of apoB-100 proteolysis by trypsin. However, less marked alterations in the peptide patterns were observed with proteinase V8 and almost none with thermolysin. This is indirect evidence that the presence of CSPG and GAG modified the exposure of polar regions of apoB-100 in LDL. Competitive binding experiments with agarose-bound heparin and soluble GAG also suggest that after formation of insoluble complexes with arterial CSPG and resolubilization the exposure of Lys, Arg-rich segments of apoB-100 is increased. Results from differential scanning calorimetry and differential thermal spectrophotometry showed that the CSPG and GAG-induced modifications reduced the thermal stability of the surface and core in LDL. If present in vivo, the structural alterations of polar segments of the LDL protein moiety may influence the outcome of its alteration with the arterial mesenchyma.     

Human nucleoporin p62 and the essential yeast nuclear pore protein NSP1 show sequence homology and a similar domain organization

NSP1 is an essential nuclear pore protein in yeast. We observed that anti-NSP1 antibodies label mammalian nuclear pore complexes and recognize nucleoporin p62. Also peptide antibodies raised against the NSP1 carboxy-terminal end cross-react with p62, a conserved component of the nuclear pore complex in higher eukaryotes. To further analyze the structural and functional similarity between NSP1 and mammalian nucleoporins, we cloned and sequenced nucleoporin p62 from a HeLa cDNA library. Human p62 consists of a carboxy-terminal domain homologous to the essential yeast NSP1 carboxy-terminal domain and an amino-terminal half resembling the repetitive middle domain of NSP1. The full-length p62 and a fusion protein consisting of cytosolic mouse dihydrofolate reductase (DHFR) and the p62 carboxy-terminal domain were expressed in transfected HeLa cells. Only overexpressed full-length p62, but not the DHFR-C-p62 fusion protein, binds wheat germ agglutinin (WGA). This suggests that modification by N-acetylglucosamine is mainly restricted to the repetitive amino-terminal half of p62 and implies a role of this type of repetitive sequences in nuclear transport. In the transfected HeLa cells, the DHFR-C-p62 fusion protein forms patchy aggregates that accumulate at the nuclear periphery but are also scattered through the cytoplasm. It is suggested that nucleoporin p62 may be targeted and anchored to the pore complex via its carboxy-terminal domain which reveals a hydrophobic heptad repeat organization similar to that found in lamins and other intermediate filament proteins.     

Nucleolar and nuclear envelope proteins of the yeast Saccharomyces cerevisiae

We have developed a fast and reliable purification protocol to obtain yeast nuclei in intact and pure form and in a reasonable yield. The purified nuclei appear homogeneous at the light and electron microscopic level, are highly enriched in the nuclear marker histone H2B and devoid of mitochondrial, vacuolar and cytosolic marker proteins. On sodium dodecyl sulfate (SDS)-polyacrylamide gels, the nuclear fraction contains unique proteins which distinguishes them from the major yeast subcellular fractions. Yeast nuclei were separated by detergent/salt extraction into soluble, insoluble and membrane fractions. Antibodies raised against subnuclear fractions lead to the identification of an integral nuclear membrane protein and a high-abundance 38-kDa protein which is located in the yeast nucleolus.     

A 40 kDa nuclear membrane protein changes its concentration and localization within the nuclear envelope of the yeast Saccharomyces cerevisiae in a cell-cycle dependent manner

In order to identify and characterize structural components in the nuclear membrane of Saccharomyces cerevisiae which show a cell-cycle dependent regulation, we have undertaken a combined biochemical/immunofluorescence microscopy approach. Antisera raised against nuclear membrane proteins from yeast lead to the identification of a 40 kDa membrane protein which cofractionated with nuclei upon cell fractionation. This 40 kDa membrane protein partitioned into the Triton X-114 phase and was not extracted from purified nuclei at alkaline pH. Using affinity-purified antibodies against this protein, the antigen was localized at the nuclear periphery suggesting that it is an integral constituent of the nuclear envelope. However, the 40 kDa antigen revealed a heterogenous distribution within the nuclear membrane: in indirect immunofluorescence microscopy, nuclei isolated from an asynchronously growing yeast culture showed either no immunodetectable antigen or contained it in a cap-, dot- or ring-like conformation. Using synchronized yeast cultures, we could demonstrate cell-cycle dependent changes of concentration and localization of the 40 kDa protein within the nuclear envelope.     

Conjugates of 5-isoquinolinesulfonylamides and oligo-D-arginine possess high affinity and selectivity towards Rho kinase (ROCK)

In the present work, conjugates of 5-isoquinolinesulfonylamides and D-arginine-rich peptides were developed into highly potent inhibitors for basophilic protein kinases. Based on Hidaka's inhibitor H9, a generic fluorescent probe ARC-1083 was constructed possessing subnanomolar dissociation constant towards several kinases of the AGC-group. Thereafter, Hidaka's inhibitor HA1077 or Fasudil was conjugated with oligo-D-arginine resulting in the compound ARC-3002 revealing high affinity towards ROCK-II (K(d)=20 pM) and over 160-fold selectivity compared to PKAc.