Heli Ruotsalainen

Glycosylation catalyzed by lysyl hydroxylase 3 is essential for basement membranes

Lysyl hydroxylase 3 (LH3) is a multifunctional enzyme possessing lysyl hydroxylase (LH), hydroxylysyl galactosyltransferase (GT) and galactosylhydroxylysyl glucosyltransferase (GGT) activities in vitro. To investigate the in vivo importance of LH3-catalyzed lysine hydroxylation and hydroxylysine-linked glycosylations, three different LH3-manipulated mouse lines were generated. Mice with a mutation that blocked only the LH activity of LH3 developed normally, but showed defects in the structure of the basement membrane and in collagen fibril organization in newborn skin and lung. Analysis of a hypomorphic LH3 mouse line with the same mutation, however, demonstrated that the reduction of the GGT activity of LH3 disrupts the localization of type IV collagen, and thus the formation of basement membranes during mouse embryogenesis leading to lethality at embryonic day (E) 9.5-14.5. Strikingly, survival of hypomorphic embryos and the formation of the basement membrane were directly correlated with the level of GGT activity. In addition, an LH3-knockout mouse lacked GGT activity leading to lethality at E9.5. The results confirm that LH3 has LH and GGT activities in vivo, LH3 is the main molecule responsible for GGT activity and that the GGT activity, not the LH activity of LH3, is essential for the formation of the basement membrane. Together our results demonstrate for the first time the importance of hydroxylysine-linked glycosylation for collagens.

Expanding the lysyl hydroxylase toolbox: new insights into the localization and activities of lysyl hydroxylase 3 (LH3).

Hydroxylysine and its glycosylated forms, galactosylhydroxylysine and glucosylgalactosylhydroxylysine, are post‐translational modifications unique to collagenous sequences. They are found in collagens and in many proteins having a collagenous domain in their structure. Since the last published reviews, significant new data have accumulated regarding these modifications. One of the lysyl hydroxylase isoforms, lysyl hydroxylase 3 (LH3), has been shown to possess three catalytic activities required sequentially to produce hydroxylysine and its glycosylated forms, that is, the lysyl hydroxylase (LH), galactosyltransferase (GT), and glucosyltransferase (GGT) activities. Studies on mouse models have revealed the importance of these different activities of LH3 in vivo. LH3 is the main molecule responsible for GGT activity in mouse embryos. A lack of this activity causes intracellular accumulation of type IV collagen, which disrupts the formation of basement membranes (BMs) during mouse embryogenesis and leads to embryonic lethality. The specific inactivation of the LH activity of LH3 causes minor alterations in the structure of the BM and collagen fibril organization, but does not affect the lifespan of mutated mice. Recent data from zebrafish demonstrate that growth cone migration depends critically on the LH3 glycosyltransferase domain. LH3 is located in the ER loosely associated with the membranes, but, unlike the other isoforms, LH3 is also found in the extracellular space in some tissues. LH3 is able to adjust the amount of hydroxylysine and hydroxylysine‐linked carbohydrates of extracellular proteins in their native conformation, suggesting that it may have a role in matrix remodeling. J. Cell. Physiol. 212: 323–329, 2007.

Serum adiponectin and resistin levels in major depressive disorder

Lehto SM, Huotari A, Niskanen L, Tolmunen T, Koivumaa‐Honkanen H, Honkalampi K, Ruotsalainen H, Herzig K‐H, Viinamäki H, Hintikka J. Serum adiponectin and resistin levels in major depressive disorder.

Serum chemokine levels in major depressive disorder

OBJECTIVE To examine the role of chemokines of two major chemokine families, CC and CXC, in major depressive disorder (MDD) in a population-based sample. METHOD The serum levels of CC chemokines MCP-1 and MIP-1beta, and CXC chemokine IL-8 were measured from 122 participants (MDD group, n=61; controls, n=61). Depression severity was assessed with the 29-item Hamilton Depression Rating Scale. RESULTS The MDD group had lower levels of MCP-1, MIP-1beta and IL-8 than the healthy controls. The likelihood of major depressive disorder for participants with chemokine levels below the median (MCP-1: < 26.26 pg/mL; MIP-1beta: < 42.57 pg/mL; IL-8: < 2.86 pg/mL) was 3.6 (p=0.002) for MIP-1beta and 2.4 (p=0.037) for IL-8 in regression models adjusted for age, gender, body mass index, smoking, and alcohol consumption. MCP-1 did not associate with the presence of MDD after adjustments for potential confounders. Further adjustments for somatic illnesses or medications did not affect these findings. CONCLUSION Our findings suggest that depression-related alterations of inflammatory markers may be more complex than previously assumed, and that at least some of the chemokines may be down-regulated.

Secretion and assembly of type IV and VI collagens depend on glycosylation of hydroxylysines.

Most lysines in type IV and VI collagens are hydroxylated and glycosylated, but the functions of these unique galactosylhydroxylysyl and glucosylgalactosylhydroxylysyl residues are poorly understood. The formation of glycosylated hydroxylysines is catalyzed by multifunctional lysyl hydroxylase 3 (LH3) in vivo, and we have used LH3-manipulated mice and cells as models to study the function of these carbohydrates. These hydroxylysine-linked carbohydrates were shown recently to be indispensable for the formation of basement membranes (Ruotsalainen, H., Sipilä, L., Vapola, M., Sormunen, R., Salo, A. M., Uitto, L., Mercer, D. K., Robins, S. P., Risteli, M., Aszodi, A., Fässler, R., and Myllylä, R. (2006) J. Cell Sci. 119, 625–635). Analysis of LH3 knock-out embryos and cells in this work indicated that loss of glycosylated hydroxylysines prevents the intracellular tetramerization of type VI collagen and leads to impaired secretion of type IV and VI collagens. Mice lacking the LH activity of LH3 produced slightly underglycosylated type IV and VI collagens with abnormal distribution. The altered distribution and aggregation of type VI collagen led to similar ultrastructural alterations in muscle to those detected in collagen VI knockout and some Ullrich congenital muscular dystrophy patients. Our results provide new information about the function of hydroxylysine-linked carbohydrates of collagens, indicating that they play an important role in the secretion, assembly, and distribution of highly glycosylated collagen types.

Characterization of cDNAs for mouse lysyl hydroxylase 1, 2 and 3, their phylogenetic analysis and tissue-specific expression in the mouse

We report on the isolation and characterization of cDNA clones for mouse lysyl hydroxylases 1, 2 and 3 (LH1, LH2, LH3). Phylogenetic analysis using nine lysyl hydroxylase sequences from five species indicates that the isoforms are derived from an ancestral gene by two duplication events, isoforms 1 and 2 being more closely related and having resulted from a more recent duplication than isoform 3. Expression of the isoforms is highly regulated in adult mouse tissues. LH1 is strongly expressed in the liver, heart, lung, skeletal muscle and kidney tissue, LH2 expression is high in the heart, lung, kidney, eye, ovary and placenta, whereas LH3 expression is high in the heart, lung, liver and testis tissue.

Lysyl Hydroxylase 3 (LH3) Modifies Proteins in the Extracellular Space, a Novel Mechanism for Matrix Remodeling

Lysyl hydroxylase 3 (LH3), the multifunctional enzyme associated with collagen biosynthesis that possesses lysyl hydroxylase and collagen glycosyltransferase activities, has been characterized in the extracellular space in this study. Lysine modifications are known to occur in the endoplasmic reticulum (ER) prior to collagen triple‐helix formation, but in this study we show that LH3 is also present and active in the extracellular space. Studies with in vitro cultured cells indicate that LH3, in addition to being an ER resident, is secreted from the cells and is found both in the medium and on the cell surface associated with collagens or other proteins with collagenous sequences. Furthermore, in vivo, LH3 is present in serum. LH3 protein levels correlate with the galactosylhydroxylysine glucosyltransferase (GGT) activity of mouse tissues. This, together with other data, indicates that LH3 is responsible for GGT activity in the tissues and that GGT activity assays can be used to quantify LH3 in tissues. LH3 in vivo is located in two compartments, in the ER and in the extracellular space, and the partitioning varies with tissue type. In mouse kidney the enzyme is located mainly intracellularly, whereas in mouse liver it is located solely in the extracellular space. The extracellular localization and the ability of LH3 to modify lysyl residues of extracellular proteins in their native, nondenaturated conformation reveals a new dynamic in extracellular matrix remodeling, suggesting a novel mechanism for adjusting the amount of hydroxylysine and hydroxylysine‐linked carbohydrates in collagenous proteins.

Reduction of Lysyl Hydroxylase 3 Causes Deleterious Changes in the Deposition and Organization of Extracellular Matrix

Lysyl hydroxylase 3 (LH3) is a multifunctional enzyme possessing lysyl hydroxylase, collagen galactosyltransferase, and glucosyltransferase (GGT) activities. We report here an important role for LH3 in the organization of the extracellular matrix (ECM) and cytoskeleton. Deposition of ECM was affected in heterozygous LH3 knock-out mouse embryonic fibroblasts (MEF+/−) and in skin fibroblasts collected from a member of a Finnish epidermolysis bullosa simplex (EBS) family known to be deficient in GGT activity. We show the GGT deficiency to be due to a transcriptional defect in one LH3 allele. The ECM abnormalities also lead to defects in the arrangement of the cytoskeleton in both cell lines. Ultrastructural abnormalities were observed in the skin of heterozygous LH3 knock-out mice indicating that even a moderate decrease in LH3 has deleterious consequences in vivo. The LH3 null allele in the EBS family member and the resulting abnormalities in the organization of the extracellular matrix, similar to those found in MEF+/−, may explain the correlation between the severity of the phenotype and the decrease in GGT activity reported in this family.

Genetic and environmental determinants of total and high-molecular weight adiponectin in families with low HDL-cholesterol and early onset coronary heart disease

OBJECTIVE Plasma adiponectin and high-density lipoprotein cholesterol (HDL-C) exhibit a well-known positive metabolic correlation. Neither heritability nor genome-wide linkage analysis for the high-molecular weight (HMW) adiponectin is available. This work estimates the genetic and environmental determinants and the heritabilities of the adiponectins and lipid traits in Finnish families with early onset coronary heart disease (CHD) and low HDL-C. METHODS Heritability and genome-wide univariate linkage analysis was performed for total and HMW adiponectin in extended families from Northern Finland with early onset CHD and low HDL-C using a variance components approach. The genetic and environmental correlations between the plasma adiponectins and various lipid traits were also studied and a bivariate analysis for HDL-C and the adiponectins carried out. RESULTS In the partial correlation analysis (adjusted for sex, age, BMI and statin use) the adiponectins showed a stronger correlation with HDL-C (total 0.57, p=0.001, HMW 0.51, p<0.005) than with any other lipid trait in unrelated subjects. Our estimates detected strong heritability for total (0.53+/-0.10), HMW (0.51+/-0.10) and the HMW/total adiponectin ratio (0.68+/-0.11). Univariate linkage analysis showed suggestive evidence of linkage on chromosome 11p15 for total adiponectin and on 3q13.2-q24 and 6p21 for the HMW adiponectin. The strongest environmental cross-correlation between the adiponectins and lipids was seen between HDL-C and total adiponectin (rhoe=0.64, p<0.05), whereas the strongest genetic correlation was detected between low-density lipoprotein cholesterol and the HMW adiponectin (rhog=-0.48, p<0.05). CONCLUSION No significant genetic correlations between HDL-C and the adiponectins were observed. Therefore, the metabolic association between HDL-C and adiponectin is most likely regulated by complex genetic pathways and environmental factors.

Serum adipokine levels in adults with a history of childhood maltreatment.

Individuals with a history of childhood maltreatment present increased rates of metabolic disturbances, but the underlying mechanisms for such phenomena are poorly understood. This study examined whether the secretion of adipokines, adipocyte-derived inflammation markers closely associated with metabolic disorders, is altered in individuals with a history of childhood maltreatment. The serum levels of inflammatory markers adiponectin and resistin were measured from 147 general population participants who had a history of adverse mental symptoms, and who also reported their experiences of childhood maltreatment. Participants with experiences of childhood maltreatment (n=30) had lowered levels of serum adiponectin (p=0.007) and resistin (p=0.028). The differences in adiponectin levels persisted in multivariate modeling with adjustments for age, gender, and body mass index (OR for each 1 standard deviation decrease in the serum adiponectin level 2.65, 95% CI 1.31-5.35, p=0.007). Additional adjustments for marital status or a diagnosis of major depressive disorder, or the exclusion of individuals using NSAIDs, oral corticosteroids, or antidepressants did not alter the results. The association between resistin levels and childhood maltreatment did not remain independent in the same models. Our findings suggest that in individuals with previously reported adverse mental symptoms, a history of childhood maltreatment is independently associated with lowered levels of the anti-inflammatory marker adiponectin. This may lead to a lowered anti-inflammatory buffer capacity, which can, in turn, increase the susceptibility to physical and psychological states characterized by pronounced pro-inflammation.