Sebastian Kalamajski

The main structural component of connective tissues is fibrillar, cross-linked collagen whose fibrillogenesis can be modulated by Small Leucine-Rich Proteins/Proteoglycans (SLRPs). Not all SLRPs’ effects on collagen and extracellular matrix in vivo have been elucidated; one of the less investigated SLRPs is asporin. Here we describe the successful...

Genetic variation at the MTIF3 (Mitochondrial Translational Initiation Factor 3) locus has been robustly associated with obesity in humans, but the functional basis behind this association is not known. Here, we applied luciferase reporter assay to map potential functional variants in the haplotype block tagged by rs1885988 and used CRISPR-Cas9 to...

Reversible phosphorylation is an important regulatory mechanism. Regulation of protein phosphorylation in β-cells has been extensively investigated, but less is known about protein dephosphorylation. To understand the role of protein dephosphorylation in β-cells and type 2 diabetes (T2D), we first examined mRNA expression of type 2C family (PP2C) o...

Background: Genetic variation at the MTIF3 (Mitochondrial Translational Initiation Factor 3) locus has been robustly associated with obesity in humans, but the functional basis behind this association is not known. Methods: Here, we applied luciferase reporter assay to map potential functional variants in the haplotype block tagged by rs1885988 and...

Obesity and type 2 diabetes are causally related, yet the underlying mechanisms are poorly defined. We aimed to subclassify obesity into etiological subtypes using a genetic-driven agnostic approach. Genetic instruments for body mass index and type 2 diabetes were classified into profiles that convey highly concordant (48 SNPs) and discordant (19 S...

Several pharmacogenetics studies have identified an association between a greater metformin-dependent reduction in HbA1c levels and the minor A allele at rs2289669 in intron 10 of SLC47A1, encoding multidrug and toxin extrusion 1 (MATE1), a presumed metformin transporter. It is currently unknown if the rs2289669 locus is a cis-eQTL, which would val...

Skeletal muscle fiber composition and capillary density influence physical performance and whole-body metabolic properties. ~45% of the variance in fiber type is heritable, which motivated us to perform a genome-wide association study of skeletal muscle histology from 656 Swedish men. Four independent variants were associated ( p < 5x10 − 8 ) with...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Metformin is the first-line pharmacotherapy for managing type 2 diabetes (T2D). However, many patients with T2D do not respond to or tolerate metformin well. Currently, there are no phenotypes that successfully predict glycemic response to, or tolerance of, metformin. We explored whether blood-based epigenetic markers could discriminate metformin r...

Lubricin (PRG4) is a mucin type protein that plays an important role in maintaining normal joint function by providing lubrication and chondroprotection. Improper lubricin modification and degradation has been observed in idiopathic osteoarthritis (OA), while the detailed mechanism still remains unknown. We hypothesized that the protease cathepsin...

Background: Chemotherapeutic efficacy can be improved by targeting the structure and function of the extracellular matrix (ECM) in the carcinomal stroma. This can be accomplished by e.g. inhibiting TGF-β1 and -β3 or treating with Imatinib, which results in scarcer collagen fibril structure in xenografted human KAT-4/HT29 (KAT-4) colon adenocarcino...

The build-up of diversified and tissue-specific assemblies of extracellular matrix (ECM) proteins depends on secreted and cell surface-located molecular arrays that coordinate ECM proteins into discrete designs. The family of small leucine-rich proteins (SLRPs) associates with and dictates the structure of fibrillar collagens, which form the backbo...

Sequences of the LRRs in (A) fibromodulin and (B) chondroadherin. The colouring scheme of the cap structures is the same as in Fig. 1. The LRR consensus is highlighted in red and the repeat length indicated in the last column.

Lubricin, a heavily O-glycosylated protein, is essential for boundary lubrication of articular cartilage. Strong surface adherence of lubricin is required given the extreme force it must withstand. Disulfide bound complexes of lubricin and cartilage oligomeric matrix protein (COMP) have recently been identified in arthritic synovial fluid suggestin...

GAG analysis chromatograms. HPLC disaccharide chromatograms of CS/DS (A), DS (B), HS (C). GAGs were purified and digested with chondroitinase ABC (A), chondroitinase B (B), or heparinases I+II+III (C), then AMAC-labeled and HPLC-separated. In (A) and (B) the disaccharide identity is: peak 1: UA-2S-GalNAc-4S (B structure); peak 2: UA-GalNAc-4S-6S (E...

Collagen molecular phenotype. (A) Two-month old dorsal skin collagen was extracted with either SDS-PAGE loading buffer or 3% acetic acid, run on 6% SDS-PAGE and stained with Coomassie Blue. The major collagen bands are denoted on the right. Similar results were obtained by analyzing nine mice of each genotype. (B) Mass spectrometry analysis of modi...

Raw data on skin collagen fibril diameter measurements. The data were collected as described in Materials and Methods, Electron microscopy. (XLSX)

Raw data from skin gene expression analysis by qPCR. The data were collected as described in Materials and Methods, Reverse transcriptase- and real-time qPCR. (XLSX)

List of Taqman probes used for qPCR skin gene expression analysis. (DOCX)

Raw data on skin biomechanics measurements. The data were collected as described in Materials and Methods, Skin tensile strength determination. (XLSX)

Tumor barrier function in carcinoma represents a major challenge to treatment and is therefore an attractive target for increasing drug delivery. Variables related to tumor barrier include aberrant blood vessels, high interstitial fluid pressure, and the composition and structure of the extracellular matrix. One of the proteins associated with dens...

Objective: Understanding the cartilage surface structure, lost in arthritic disease, is essential for developing strategies to effectively restore it. Given that adherence of the lubricating protein, lubricin, to the cartilage surface is critical for boundary lubrication, an interaction with cartilage oligomeric matrix protein (COMP) was investiga...

The small leucine-rich proteoglycans (SLRPs) are important regulators of extracellular matrix assembly and cell signalling. We have determined crystal structures at ~2.2 Å resolution of human fibromodulin and chondroadherin, two collagen-binding SLRPs. Their overall fold is similar to that of the prototypical SLRP, decorin, but unlike decorin neith...

Small leucine rich proteoglycans interact with other extracellular matrix proteins and are important regulators of matrix assembly. Fibromodulin has a key role in connective tissues, binding collagen through two identified binding sites in its leucine rich repeat domain and regulating collagen fibril formation in vitro and in vivo. Some nine tyrosi...

A typical obstacle to cancer therapy is the limited distribution of low-molecular weight anti-cancer drugs within the carcinoma tissue. In experimental carcinoma, Imatinib (STI571) increases efficacy of synchronized chemotherapy, reduces tumor interstitial fluid pressure and increases interstitial fluid volume. STI571 also increases the water-perfu...

The hallmark of fibrotic disorders is a highly cross-linked and dense collagen matrix, a property driven by the oxidative action of lysyl oxidase. Other fibrosis-associated proteins also contribute to the final collagen matrix properties, one of which is fibromodulin - its interactions with collagen affect collagen cross-linking, packing, and fibri...

The constitution and biophysical properties of extracellular matrices can dramatically influence cellular phenotype during development, homeostasis, or pathogenesis. These effects can be signaled through a differentially regulated assembly of collagen fibrils, orchestrated by a family of collagen-associated Small Leucine-Rich Proteins, SLRPs. In th...

The controlled assembly of collagen monomers into fibrils, with accompanying intermolecular cross-linking by lysyl oxidase-mediated bonds, is vital to the structural and mechanical integrity of connective tissues. This process is influenced by collagen-associated proteins, including Small Leucine-Rich Proteins (SLRPs), but the regulatory mechanisms...

Objective: The aim of this study was to analyze how an altered collagen structure affects development of atherosclerotic plaques. Methods and results: Fibromodulin-null mice develop an abnormal collagen fibril structure. In apolipoprotein E (ApoE)-null and ApoE/fibromodulin-null mice, a shear stress-modifying carotid artery cast induced formatio...

Spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic type (lepto-SEMDJL, aka SEMDJL, Hall type), is an autosomal dominant skeletal disorder that, in spite of being relatively common among skeletal dysplasias, has eluded molecular elucidation so far. We used whole-exome sequencing of five unrelated individuals with lepto-SEMDJL to ident...

Collagen fibers expose distinct domains allowing for specific interactions with other extracellular matrix proteins and cells. To investigate putative collagen domains that govern integrin α(V)β(3)-mediated cellular interactions with native collagen fibers we took advantage of the streptococcal protein CNE that bound native fibrillar collagens. CNE...

Monoclonal antibody-based therapies have made an important contribution to current treatment strate-gies for cancer and autoimmune disease. However, the cost for these new drugs puts a significant strain on the health-care economy, resulting in limited availability for patients. Therapeutic vaccination, defined as induction of immu-nity against a d...

Monoclonal antibody-based therapies have made an important contribution to current treatment strategies for cancer and autoimmune disease. However, the cost for these new drugs puts a significant strain on the health-care economy, resulting in limited availability for patients. Therapeutic vaccination, defined as induction of immunity against a dis...

To study the presence of interferogenic autoantibodies in systemic sclerosis (SSc) and their correlation with clinical manifestations, serum levels of interferon alpha (IFNalpha) and chemokines of importance in the disease process. Peripheral blood mononuclear cells (PBMCs) or purified plasmacytoid dendritic cells (pDCs) from healthy donors were st...

Small leucine-rich proteoglycans/proteins (SLRPs) are associated with collagen fibril formation, and therefore important for the proper formation of extracellular matrices. SLRPs are differentially expressed in tissues and during pathological conditions, contributing to the development of connective tissue properties. The binding of SLRPs to collag...

Dermatan sulfate epimerase 1 (DS-epi1) and DS-epi2 convert glucuronic acid to iduronic acid in chondroitin/dermatan sulfate biosynthesis. Here we report on the generation of DS-epi1-null mice and the resulting alterations in the chondroitin/dermatan polysaccharide chains. The numbers of long blocks of adjacent iduronic acids are greatly decreased i...

The interactions of the ECM (extracellular matrix) protein asporin with ECM components have previously not been investigated. Here, we show that asporin binds collagen type I. This binding is inhibited by recombinant asporin fragment LRR (leucine-rich repeat) 10-12 and by full-length decorin, but not by biglycan. We demonstrate that the polyasparta...

Few studies are performed on the sustainability of the pelvic floor extracellular matrix important for preventing development of pelvic organ prolapse (POP). Collagens I and III, the elastin-associated proteins fibrillin-1 and fibulin-5 and the small leucine-rich repeat proteoglycans (SLRPs) decorin, lumican and fibromodulin are involved in giving...

Lumican and fibromodulin compete for collagen type I binding in vitro, and fibromodulin-deficient mice have 4-fold more lumican in tendons. These observations indicate that homologous sequences in lumican and fibromodulin bind to collagen type I. Here, we demonstrate that lumican binding to collagen type I is mediated mainly by Asp-213 in leucine-r...

Mutations in the gene encoding laminin α2 chain cause congenital muscular dystrophy type 1A. In skeletal muscle, laminin α2 chain binds at least two receptor complexes: the dystrophin-glycoprotein complex and integrin α7β1. To gain insight into the molecular mechanisms underlying this disorder, we performed gene expression profiling of laminin α2 c...

Fibromodulin belongs to the small leucine-rich repeat proteoglycan family, interacts with collagen type I, and controls collagen fibrillogenesis and assembly. Here, we show that a major fibromodulin-binding site for collagen type I is located in leucine-rich repeat 11 in the C terminus of the leucine-rich repeat domain. We identified Glu-353 and Ly...

Research on the biology of the tumor stroma has the potential to lead to development of more effective treatment regimes enhancing the efficacy of drug-based treatment of solid malignancies. Tumor stroma is characterized by distorted blood vessels and activated connective tissue cells producing a collagen-rich matrix, which is accompanied by elevat...

Decorin belongs to the small leucine-rich repeat proteoglycan family, interacts with fibrillar collagens, and regulates the assembly, structure, and biomechanical properties of connective tissues. The decorin-collagen type I-binding region is located in leucine-rich repeats 5-6. Site-directed mutagenesis of this 54-residue-long collagen-binding seq...

The N-terminal fragment (FNZN) of the fibronectin-binding protein FNZ from Streptococcus equi subspecies zooepidemicus was investigated as to effects on murine cell interactions with extracellular matrix proteins. FNZN bound to immobilized fibronectin (FN) and native, but not denatured, collagen type I. FNZN had no effect on primary adhesion of cel...