LDL cholesterol targets rarely achieved in familial hypercholesterolemia patients: A sex and gender-specific analysis.

BACKGROUND AND AIMS: Despite lipid lowering therapy (LLT), reaching LDL-C targets in patients with familial hypercholesterolemia (FH) remains challenging. Our aim was to determine attainment of LDL-C target levels and reasons for not reaching these in female and male FH patients. METHODS: We performed a cross-sectional study of heterozygous FH patients in five hospitals in the Netherlands and Norway. Clinical characteristics and information about LLT, lipid levels and reasons for not being on LDL-C treatment target were retrospectively collected from electronic medical records. RESULTS: We studied 3178 FH patients (53.9% women), median age 48.0 (IQR 34.0-59.9) years. Median LDL-C before treatment and on-treatment was higher in women compared to men (6.2 (IQR 5.1-7.3) and 6.0 (IQR 4.9-7.2) mmol/l (p=0.005) and 3.0 (IQR 2.4-3.8) and 2.8 (IQR 2.3-3.5) mmol/L (p<0.001)), respectively. A minority of women (26.9%) and men (28.9%) reached LDL-C target. In patients with CVD, 17.2% of women and 25.8% of men reached LDL-C target. Women received less often high-intensity statins and ezetimibe. Most common reported reasons for not achieving the LDL-C target were insufficient effect of maximum LLT (women 17.3%, men 24.3%) and side effects (women 15.2%, men 8.6%). CONCLUSIONS: In routine practice, only a minority of women and men with FH achieved their LDL-C treatment target. Extra efforts have to be made to provide FH patients with reliable information on the safety of statins and their long-term effects on CVD risk reduction. If statin treatment is insufficient, alternative lipid lowering therapies such as ezetimibe or PCSK9-inhibitors should be considered.

MtGimC, a novel archaeal chaperone related to the eukaryotic chaperonin cofactor GimC/prefoldin.

Group II chaperonins in the eukaryotic and archaeal cytosol assist in protein folding independently of the GroES-like cofactors of eubacterial group I chaperonins. Recently, the eukaryotic chaperonin was shown to cooperate with the hetero-oligomeric protein complex GimC (prefoldin) in folding actin and tubulins. Here we report the characterization of the first archaeal homologue of GimC, from Methanobacterium thermoautotrophicum. MtGimC is a hexamer of 87 kDa, consisting of two alpha and four beta subunits of high alpha-helical content that are predicted to contain extended coiled coils and represent two evolutionarily conserved classes of Gim subunits. Reconstitution experiments with MtGimC suggest that two subunits of the alpha class (archaeal Gimalpha and eukaryotic Gim2 and 5) form a dimer onto which four subunits of the beta class (archaeal Gimbeta and eukaryotic Gim1, 3, 4 and 6) assemble. MtGimalpha and beta can form hetero-complexes with yeast Gim subunits and MtGimbeta partially complements yeast strains lacking Gim1 and 4. MtGimC is a molecular chaperone capable of stabilizing a range of non-native proteins and releasing them for subsequent chaperonin-assisted folding. In light of the absence of Hsp70 chaperones in many archaea, GimC may fulfil an ATP-independent, Hsp70-like function in archaeal de novo protein folding.

Epitope tagging of yeast genes using a PCR-based strategy: more tags and improved practical routines.

Epitope tagging of proteins as a strategy for the analysis of function, interactions and the subcellular distribution of proteins has become widely used. In the yeast Saccharomyces cerevisiae, molecular biological techniques have been developed that use a simple PCR-based strategy to introduce epitope tags to chromosomal loci (Wach et al., 1994). To further employ the power of this strategy, a variety of novel tags was constructed. These tags were combined with different selectable marker genes, resulting in PCR amplificable modules. Only one set of primers is required for the amplification of any module. Furthermore, convenient laboratory techniques are described that facilitate the genetic manipulations of yeast strains, as well as the analysis of the epitope-tagged proteins.

Compartmentation of protein folding in vivo: sequestration of non-native polypeptide by the chaperonin-GimC system.

The functional coupling of protein synthesis and chaperone-assisted folding in vivo has remained largely unexplored. Here we have analysed the chaperonin-dependent folding pathway of actin in yeast. Remarkably, overexpression of a heterologous chaperonin which traps non-native polypeptides does not interfere with protein folding in the cytosol, indicating a high-level organization of folding reactions. Newly synthesized actin avoids the chaperonin trap and is effectively channelled from the ribosome to the endogenous chaperonin TRiC. Efficient actin folding on TRiC is critically dependent on the hetero-oligomeric co-chaperone GimC. By interacting with folding intermediates and with TRiC, GimC accelerates actin folding at least 5-fold and prevents the premature release of non-native protein from TRiC. We propose that TRiC and GimC form an integrated 'folding compartment' which functions in cooperation with the translation machinery. This compartment sequesters newly synthesized actin and other aggregation-sensitive polypeptides from the crowded macromolecular environment of the cytosol, thereby allowing their efficient folding.

A novel protein complex promoting formation of functional alpha- and gamma-tubulin.

We describe the identification of GIM1/YKE2, GIM2/PAC10, GIM3, GIM4 and GIM5 in a screen for mutants that are synthetically lethal with tub4-1, encoding a mutated yeast gamma-tubulin. The cytoplasmic Gim proteins encoded by these GIM genes are present in common complexes as judged by co-immunoprecipitation and gel filtration experiments. The disruption of any of these genes results in similar phenotypes: the gim null mutants are synthetically lethal with tub4-1 and super-sensitive towards the microtubule-depolymerizing drug benomyl. All except Deltagim4 are cold-sensitive and their microtubules disassemble at 14 degrees C. The Gim proteins have one function related to alpha-tubulin and another to Tub4p, supported by the finding that the benomyl super-sensitivity is caused by a reduced level of alpha-tubulin while the synthetic lethality with tub4-1 is not. In addition, GIM1/YKE2 genetically interacts with two distinct classes of genes, one of which is involved in tubulin folding and the other in microtubule nucleation. We show that the Gim proteins are important for Tub4p function and bind to overproduced Tub4p. The mammalian homologues of GIM1/YKE2 and GIM2/PAC10 rescue the synthetically lethal phenotype with tub4-1 as well as the cold-sensitivity and benomyl super-sensitivity of the yeast deletion mutants. We suggest that the Gim proteins form a protein complex that promotes formation of functional alpha- and gamma-tubulin.

Biosynthesis of lantibiotic nisin. Posttranslational modification of its prepeptide occurs at a multimeric membrane-associated lanthionine synthetase complex.

The lantibiotic nisin of Lactococcus lactis is matured from a ribosomally synthesized prepeptide by postranslational modification. Genetic and biochemical evidence suggests that genes nisB and nisC of the nisin gene cluster encode proteins necessary for prenisin modification. Inactivation of both genes resulted in complete loss of nisin production. The preparation of membrane vesicles revealed that NisB and NisC are attached to the cellular membrane, and co-immunoprecipitation experiments showed that they are associated with each other. By using the yeast two-hybrid system, which is a highly sensitive method to unravel protein-protein interactions, we could show that the nisin prepeptide physically interacts with the NisC protein, suggesting that NisC contains a binding site for prenisin. This was also confirmed by co-immunoprecipitation of the NisC protein and the NisA prepeptide by antibodies directed against the leader sequence of the nisin prepeptide. The two-hybrid analysis also confirmed the interaction between NisB and NisC as well as the interaction between NisB and NisC as well as the interaction between NisC and the NisT ABC transporter. A minor interaction was also indicated between prenisin and the NisB protein. Furthermore, the two-hybrid investigations also revealed that at least two molecules of NisC and two molecules of NisT are part of the modification and transport complex. Our results suggest that lantibiotic maturation and secretion occur at a membrane-associated multimeric lanthionine synthetase complex consisting of proteins NisB, NisC, and the ABC transporter molecules NisT.

Genes involved in immunity to the lantibiotic nisin produced by Lactococcus lactis 6F3.

The lantibiotic nisin is produced by several strains of Lactococcus lactis. The complete gene cluster for nisin biosynthesis in L. lactis 6F3 comprises 15 kb of DNA. As described previously, the structural gene nisA is followed by the genes nisB, nisT, nisC, nisI, nisP, nisR, and nisK. Further analysis revealed three additional open reading frames, nisF, nisE, and nisG, adjacent to nisK. Approximately 1 kb downstream of the nisG gene, three open reading frames in the opposite orientation have been identified. One of the reading frames, sacR, belongs to the sucrose operon, indicating that all genes belonging to the nisin gene cluster of L. lactis 6F3 have now been identified. Proteins NisF and NisE show strong homology to members of the family of ATP-binding cassette (ABC) transporters, and nisG encodes a hydrophobic protein which might act similarly to the immunity proteins described for several colicins. Gene disruption mutants carrying mutations in the genes nisF, nisE, and nisG were still able to produce nisin. However, in comparison with the wild-type strain, these mutants were more sensitive to nisin. This indicates that besides nisI the newly identified genes are also involved in immunity to nisin. The NisF-NisE ABC transporter is homologous to an ABC transporter of Bacillus subtilis and the MbcF-MbcE transporter of Escherichia coli, which are involved in immunity to subtilin and microcin B17, respectively.

Regulation of nisin biosynthesis and immunity in Lactococcus lactis 6F3.

The biosynthetic genes of the nisin-producing strain Lactococcus lactis 6F3 are organized in an operon-like structure starting with the structural gene nisA followed by the genes nisB, nisT, and nisC, which are probably involved in chemical modification and secretion of the prepeptide (G. Engelke, Z. Gutowski-Eckel, M. Hammelmann, and K.-D. Entian, Appl. Environ. Microbiol. 58:3730-3743, 1992). Subcloning of an adjacent 5-kb downstream region revealed additional genes involved in nisin biosynthesis. The gene nisI, which encodes a lipoprotein, causes increased immunity after its transformation into nisin-sensitive L. lactis MG1614. It is followed by the gene nisP, coding for a subtilisin-like serine protease possibly involved in processing of the secreted leader peptide. Adjacent to the 3' end of nisP the genes nisR and nisK were identified, coding for a regulatory protein and a histidine kinase, showing marked similarities to members of the OmpR/EnvZ-like subgroup of two-component regulatory systems. The deduced amino acid sequences of nisR and nisK exhibit marked similarities to SpaR and SpaK, which were recently identified as the response regulator and the corresponding histidine kinase of subtilin biosynthesis. By using antibodies directed against the nisin prepeptide and the NisB protein, respectively, we could show that nisin biosynthesis is regulated by the expression of its structural and biosynthetic genes. Prenisin expression starts in the exponential growth phase and precedes that of the NisB protein by approximately 30 min. Both proteins are expressed to a maximum in the stationary growth phase.

Growth phase-dependent regulation and membrane localization of SpaB, a protein involved in biosynthesis of the lantibiotic subtilin.

The information responsible for biosynthesis of the lantibiotic subtilin is organized in an operon-like structure that starts with the spaB gene. The spaB gene encodes an open reading frame consisting of 1,030 amino acid residues, and it was calculated that a protein having a theoretical molecular mass of 120.5 kDa could be produced from this gene. This is consistent with the apparent molecular weight for SpaB of 115,000 which was estimated after sodium dodecyl sulfate-gel electrophoresis and identification with SpaB-specific antibodies. The SpaB protein is very similar to proteins EpiB and NisB, which were identified previously as being involved in epidermin and nisin biosynthesis. Upstream from SpaB a characteristic sigma A promoter sequence was identified. An immunoblot analysis revealed that SpaB expression was strongly regulated. No SpaB protein was detected in the early logarithmic growth phase, and maximum SpaB expression was observed in the early stationary growth phase. The expression of SpaB was strongly correlated with subtilin biosynthesis. Deletion mutations in either of two recently identified regulatory genes, spaR and spaK, which act as a "two-component" regulatory system necessary for growth phase-dependent induction of subtilin biosynthesis (C. Klein, C. Kaletta, and K. D. Entian, Appl. Environ. Microbiol. 59:296-303, 1993), also resulted in failure of SpaB expression. To investigate the intracellular localization of SpaB, vesicles of Bacillus subtilis were prepared. The SpaB protein cosedimented with the vesicle fraction and was released only after vigorous resuspension of the vesicles. Our results suggest that SpaB is membrane associated and that subtilin biosynthesis occurs at the cytoplasmic membrane of B. subtilis.