Disrupted protein interaction dynamics in a genetic neurodevelopmental disorder revealed by structural bioinformatics and genetic code expansion

Deciphering the structural effects of gene variants is essential for understanding the pathophysiological mechanisms of genetic diseases. Using a neurodevelopmental disorder called Bosch-Boonstra-Schaaf Optic Atrophy Syndrome (BBSOAS) as a genetic disease model, we applied structural bioinformatics and Genetic Code Expansion (GCE) strategies to assess the pathogenic impact of human NR2F1 variants and their binding with known and novel partners. While the computational analyses of the NR2F1 structure delineated the molecular basis of the impact of several variants on the isolated and complexed structures, the GCE enabled covalent and site-specific capture of transient supramolecular interactions in living cells. This revealed the variable quaternary conformations of NR2F1 variants and highlighted the disrupted interplay with dimeric partners and the newly identified co-factor, CRABP2. The disclosed consequence of the pathogenic mutations on the conformation, supramolecular interplay, and alterations in the cell cycle, viability, and sub-cellular localization of the different variants reflect the heterogeneous disease spectrum of BBSOAS and set up novel foundation for unveiling the complexity of neurodevelopmental diseases.

Impact of calmodulin missense variants associated with congenital arrhythmia on the thermal stability and the degree of unfolding

Thermal denaturation profiles of proteins that bind several ligands may deviate from the single transition, making their thermodynamic description challenging. We report an empirical method that estimates melting temperatures (Tm) from multi-transition thermal denaturation profiles of 16 variants of calmodulin (CaM) associated with congenital arrhythmia. Differences in Tm estimated by empirical fitting correlate (for apo CaM variants) with those obtained by thermodynamic models. Most CaM variants were more stable than the wild type (WT) in the absence of Ca2+, but less stable in the presence of Ca2+, and displayed either WT-like or higher unfolding percentages in their apo-form, as evaluated by circular dichroism spectroscopy.

Recombinant protein delivery enables modulation of the phototransduction cascade in mouse retina

Inherited retinal dystrophies are often associated with mutations in the genes involved in the phototransduction cascade in photoreceptors, a paradigmatic signaling pathway mediated by G protein-coupled receptors. Photoreceptor viability is strictly dependent on the levels of the second messengers cGMP and Ca2+. Here we explored the possibility of modulating the phototransduction cascade in mouse rods using direct or liposome-mediated administration of a recombinant protein crucial for regulating the interplay of the second messengers in photoreceptor outer segments. The effects of administration of the free and liposome-encapsulated human guanylate cyclase-activating protein 1 (GCAP1) were compared in biological systems of increasing complexity (in cyto, ex vivo, and in vivo). The analysis of protein biodistribution and the direct measurement of functional alteration in rod photoresponses show that the exogenous GCAP1 protein is fully incorporated into the mouse retina and photoreceptor outer segments. Furthermore, only in the presence of a point mutation associated with cone-rod dystrophy in humans p.(E111V), protein delivery induces a disease-like electrophysiological phenotype, consistent with constitutive activation of the retinal guanylate cyclase. Our study demonstrates that both direct and liposome-mediated protein delivery are powerful complementary tools for targeting signaling cascades in neuronal cells, which could be particularly important for the treatment of autosomal dominant genetic diseases.

Ionic displacement of Ca2+ by Pb2+ in calmodulin is affected by arrhythmia-associated mutations

Lead is a highly toxic metal that severely perturbs physiological processes even at sub-micromolar levels, often by disrupting the Ca²⁺ signaling pathways. Recently, Pb²⁺-associated cardiac toxicity has emerged, with potential involvement of both the ubiquitous Ca²⁺ sensor protein calmodulin (CaM) and ryanodine receptors. In this work, we explored the hypothesis that Pb²⁺ contributes to the pathological phenotype of CaM variants associated with congenital arrhythmias. We performed a thorough spectroscopic and computational characterization of CaM conformational switches in the co-presence of Pb²⁺ and four missense mutations associated with congenital arrhythmias, namely N53I, N97S, E104A and F141L, and analyzed their effects on the recognition of a target peptide of RyR2. When bound to any of the CaM variants, Pb²⁺ is difficult to displace even under equimolar Ca²⁺ concentrations, thus locking all CaM variants in a specific conformation, which exhibits characteristics of coiled-coil assemblies. All arrhythmia-associated variants appear to be more susceptible to Pb²⁺ than WT CaM, as the conformational transition towards the coiled-coil conformation occurs at lower Pb²⁺, regardless of the presence of Ca²⁺, with altered cooperativity. The presence of arrhythmia-associated mutations specifically alters the cation coordination of CaM variants, in some cases involving allosteric communication between the EF-hands in the two domains. Finally, while wild type CaM increases the affinity for the RyR2 target in the presence of Pb²⁺, no specific pattern could be detected for all other variants, ruling out a synergistic effect of Pb²⁺ and mutations in the recognition process.

Biallelic Variants in TULP1 Are Associated with Heterogeneous Phenotypes of Retinal Dystrophy

Biallelic pathogenic variants in TULP1 are mostly associated with severe rod-driven inherited retinal degeneration. In this study, we analyzed clinical heterogeneity in 17 patients and characterized the underlying biallelic variants in TULP1. All patients underwent thorough ophthalmological examinations. Minigene assays and structural analyses were performed to assess the consequences of splice variants and missense variants. Three patients were diagnosed with Leber congenital amaurosis, nine with early onset retinitis pigmentosa, two with retinitis pigmentosa with an onset in adulthood, one with cone dystrophy, and two with cone-rod dystrophy. Seventeen different alleles were identified, namely eight missense variants, six nonsense variants, one in-frame deletion variant, and two splice site variants. For the latter two, minigene assays revealed aberrant transcripts containing frameshifts and premature termination codons. Structural analysis and molecular modeling suggested different degrees of structural destabilization for the missense variants. In conclusion, we report the largest cohort of patients with TULP1-associated IRD published to date. Most of the patients exhibited rod-driven disease, yet a fraction of the patients exhibited cone-driven disease. Our data support the hypothesis that TULP1 variants do not fold properly and thus trigger unfolded protein response, resulting in photoreceptor death.

Calmodulin variants associated with congenital arrhythmia impair selectivity for ryanodine receptors

Among its many molecular targets, the ubiquitous calcium sensor protein calmodulin (CaM) recognizes and regulates the activity of ryanodine receptors type 1 (RyR1) and 2 (RyR2), mainly expressed in skeletal and cardiac muscle, respectively. Such regulation is essential to achieve controlled contraction of muscle cells. To unravel the molecular mechanisms underlying the target recognition process, we conducted a comprehensive biophysical investigation of the interaction between two calmodulin variants associated with congenital arrhythmia, namely N97I and Q135P, and a highly conserved calmodulin-binding region in RyR1 and RyR2. The structural, thermodynamic, and kinetic properties of protein-peptide interactions were assessed together with an in-depth structural and topological investigation based on molecular dynamics simulations. This integrated approach allowed us to identify amino acids that are crucial in mediating allosteric processes, which enable high selectivity in molecular target recognition. Our results suggest that the ability of calmodulin to discriminate between RyR1 an RyR2 targets depends on kinetic discrimination and robust allosteric communication between Ca²⁺-binding sites (EF1-EF3 and EF3-EF4 pairs), which is perturbed in both N97I and Q135P arrhythmia-associated variants.

AB0936 Neuropathic pain in Psoriatic Arthritis: analysis of populations treated with anti TNF and anti IL17

Background

Psoriatic arthritis (PsA) is a disease characterized by chronic pain and it is often associated with the presence of fibromyalgia (FMS) with an estimated prevalence of 18%. Several studies demonstrated the central role of neuropathic pain in FMS. However, patients with inflammatory diseases such as PsA frequently complain of complex pain symptoms, with neuropathic characteristics. Therefore, in PsA we can recognize both an inflammatory pain and a neuropathic pain that can be exacerbated both by the concomitant fibromyalgia or depending only on the PsA itself. In fact, In the context of PsA, the presence of neuropathic pain features has been documented in 28% of patients. This could be a reason why the low remission rate in these patients. Finally, Studies on murin models revealed a possible role of IL17, key cytokine of PsA pathogenesis, in mechanism of neuropathic pain.

Objectives

To evaluate the role of anti-TNF and antiIL-17 in neuropathic pain in PsA patients treated with the first biological drug (bDMARDS).

Methods

A cross-sectional evaluation was conducted on 38 PsA patients classified by Classification criteria for Psoriatic Arthritis (CASPAR), referred to the PsA outpatient clinic of “University of Campania Luigi Vanvitelli”. Thirty patients were treated with anti-TNF (mean age 53 years, 17F, 13M), 8 were treated with anti-IL17 (mean age 50 years, 5F, 3M), for almost 6 months. For each patient, an assessment of disease activity using DAPSA and physical function was carried out. The presence of comorbid fibromyalgia syndrome (FMS) was evaluated according to ACR 2016 criteria. We investigated neuropathic pain features through the PainDETECT Questionnaire (PDQ).

Results

Nine patients treated with anti TNF were in DAPSA remission; 18 patients had low disease activity, 3 had High disease activity, FMS was detected in 11 of 30 patients, no one in DAPSA remission for PsA. Characteristics of neuropathic pain (PDQ ≥ 19) were found in 13 (43.3%) patients overall; unlikely neuropathic pain (PDQ < 12) in 16 (53.3%) patients. In the first group 7 patients had FMS, in the second group 3 had FMS. So, our analysis revealed the presence of neuropathic pain in 6 patients (54,5%) with PsA treated with antiTNF with no FMS; all of them were in low disease activity. The same analysis was conducted on anti IL17 treated population: 4 patients were in DAPSA remission, 2 patients in low disease activity, 2 patients in high, disease activity. FMS was diagnosed in 3 patients, 1 of them was in DAPSA remission for PsA. PDQ>19 was found only in 1 patient, who had FMS in comorbidity; the others had no neuropathic pain. So, we had no PsA patient treated with antiIL17, that manifested symptoms of neuropathic pain.

Conclusion

The contribute of IL-17 in developing of neuropathic pain suggests the possible role of anti IL17 as therapy; our results support this tesis suggesting a possible role of anti IL17 in treatment of neuropathic pain. A limit to our work is given by the low sample size for which further studies are necessary to confirm this data.

References

[1]Ramjeeawon A, Neuropathic-like pain in psoriatic arthritis: evidence of abnormal pain processing. Clin Rheumatol. 2019;

[2]Sun C, IL-17 contributed to the neuropathic pain following peripheral nerve injury by promoting astrocyte proliferation and secretion of proinflammatory cytokines. Mol Med Rep. 2017

[3]Martinez-Lavin M: Fibromyalgia is a neuropathic pain syndrome. J Rheumatol 2006;

Disclosure of Interests

None declared

AB1198 PREVALENCE AND PSYCHOPATHOLOGICAL CHARACTERISTICS OF ANXIETY AND DEPRESSIVE SYMPTOMS IN FIBROMYALGIA PATIENTS

Background

Several studies reported higher depression and anxiety rates in fibromyalgia (FM) patients compared to the general population. Furthermore, dysfunctional coping strategies

have been pointed to as intrinsic parts of the pathogenesis of FM.

Objectives

Our study aimed to verify the prevalence of anxiety and depressive symptoms and explore their correlation with physical symptoms as fatigue, sleep, and widespread pain in a cohort of patients diagnosed with FM. We also aimed to determine whether dysfunctional coping strategies might increase the depression and anxiety burden, besides worsening the core symptoms of FM.

Methods

We analyzed a cohort of 105 patients (median age of 53 years 6 M, 99 F) with a diagnosis of FM according to the ACR 2016 criteria. The participants were consecutively recruited from the Fibromyalgia clinic of the University of Campania “Luigi Vanvitelli”. All patients underwent a psychiatric evaluation. We assessed widespread pain by the Widespread Pain Index (WPI) and the presence of fatigue by the Symptom Severity score (SS). Sleep disorders were investigated through Pittsburgh Sleep Quality Index (PSQI). We analyzed mental alterations by Hamilton Depression and Anxiety Rating Scales (HAM-D, HAM-A), and coping strategies by Coping Orientation to Problems Experienced (COPE) Inventory.

The Statistical Package for Social Sciences (SPSS) 22.0 was used; the level of significance was set at p < 0.05.

Results

All patients showed fatigue and widespread pain (100%); sleep disturbances were found in 90.5% of patients and overlapped with all sleep phases. The prevalence of anxiety associated with depression was 75.2%. We found isolated anxiety in 14.3% and isolated depression in 4.8% of patients. We further evidenced a different degree of depression: mild (50.7%), moderate (24.3%), and severe (6.5%). All patients showed depressed mood only if questioned (low tendency to spontaneous verbalization). COPE analysis showed no significant differences in the use of the three coping strategies (Problem-focused, emotion-focused, avoidance-focused). Pearson’s correlation analysis highlighted a negative relationship between problem-focused strategies and the severity of anxiety (r = -0.31, p = .001) and depression (r = -0.32, p = .001). Our analysis also highlighted a positive correlation between fatigue, sleep disturbances, widespread pain, and both anxiety and depression. The analysis of the characteristics of anxiety and depressive symptoms showed a scarce tendency to spontaneous verbalization of depressed mood and ideas of guilt, mostly limited to family relationships, and a sense of ineffectiveness conditioned by the physical symptoms of the disease. Most patients showed psychomotor agitation, psychic and somatic anxiety, poor insight. The analysis of coping strategies adopted showed a negative correlation between problem-focused strategies and anxiety-depressive symptoms, suggesting that such strategies are less frequent in FM patients with comorbid anxiety and depressive symptoms.

Conclusion

Our study confirms the high prevalence of anxiety and depressive symptoms in FM patients. A positive correlation between the pivotal symptoms and anxiety and depressive symptoms may suggest, without implying a cause-and-effect relationship, that psychiatric intervention should be considered along with rheumatologic treatment, to improve both physical symptoms and quality of life. Potentiating problem-focused coping strategies may represent a target to improve anxiety and depressive symptoms.

References

[1]Wolfe et al Revisions to the 2010/2011 FM diagnostic criteria. Semin Arth. Rheum. 2016

Table 1.

Correlation analysis between coping strategies and HAM-D and HAM-A total scores

HAM-DHAM- AProblem-focused Coping- 0,32**- 0,31**Avoidant Coping0,800,92Emotion Coping0,140,13

**p<0.01

Disclosure of Interests

None declared

Molecular Properties of Human Guanylate Cyclase-Activating Protein 3 (GCAP3) and Its Possible Association with Retinitis Pigmentosa

The cone-specific guanylate cyclase-activating protein 3 (GCAP3), encoded by the GUCA1C gene, has been shown to regulate the enzymatic activity of membrane-bound guanylate cyclases (GCs) in bovine and teleost fish photoreceptors, to an extent comparable to that of the paralog protein GCAP1. To date, the molecular mechanisms underlying GCAP3 function remain largely unexplored. In this work, we report a thorough characterization of the biochemical and biophysical properties of human GCAP3, moreover, we identified an isolated case of retinitis pigmentosa, in which a patient carried the c.301G>C mutation in GUCA1C, resulting in the substitution of a highly conserved aspartate residue by a histidine (p.(D101H)). We found that myristoylated GCAP3 can activate GC1 with a similar Ca2+-dependent profile, but significantly less efficiently than GCAP1. The non-myristoylated form did not induce appreciable regulation of GC1, nor did the p.D101H variant. GCAP3 forms dimers under physiological conditions, but at odds with its paralogs, it tends to form temperature-dependent aggregates driven by hydrophobic interactions. The peculiar properties of GCAP3 were confirmed by 2 ms molecular dynamics simulations, which for the p.D101H variant highlighted a very high structural flexibility and a clear tendency to lose the binding of a Ca2+ ion to EF3. Overall, our data show that GCAP3 has unusual biochemical properties, which make the protein significantly different from GCAP1 and GCAP2. Moreover, the newly identified point mutation resulting in a substantially unfunctional protein could trigger retinitis pigmentosa through a currently unknown mechanism.

Alterations in calmodulin-cardiac ryanodine receptor molecular recognition in congenital arrhythmias

Calmodulin (CaM), a ubiquitous and highly conserved Ca²⁺-sensor protein involved in the regulation of over 300 molecular targets, has been recently associated with severe forms of lethal arrhythmia. Here, we investigated how arrhythmia-associated mutations in CaM localized at the C-terminal lobe alter the molecular recognition with Ryanodine receptor 2 (RyR2), specifically expressed in cardiomyocytes. We performed an extensive structural, thermodynamic, and kinetic characterization of the variants D95V/H in the EF3 Ca²⁺-binding motif and of the D129V and D131H/E variants in the EF4 motif, and probed their interaction with RyR2. Our results show that the specific structural changes observed for individual CaM variants do not extend to the complex with the RyR2 target. Indeed, some common alterations emerge at the protein–protein interaction level, suggesting the existence of general features shared by the arrhythmia-associated variants. All mutants showed a faster rate of dissociation from the target peptide than wild-type CaM. Integration of spectroscopic data with exhaustive molecular dynamics simulations suggests that, in the presence of Ca²⁺, functional recognition involves allosteric interactions initiated by the N-terminal lobe of CaM, which shows a lower affinity for Ca²⁺ compared to the C-terminal lobe in the isolated protein.

A Novel GUCA1A Variant Associated with Cone Dystrophy Alters cGMP Signaling in Photoreceptors by Strongly Interacting with and Hyperactivating Retinal Guanylate Cyclase

Guanylate cyclase-activating protein 1 (GCAP1), encoded by the GUCA1A gene, is a neuronal calcium sensor protein involved in shaping the photoresponse kinetics in cones and rods. GCAP1 accelerates or slows the cGMP synthesis operated by retinal guanylate cyclase (GC) based on the light-dependent levels of intracellular Ca²⁺, thereby ensuring a timely regulation of the phototransduction cascade. We found a novel variant of GUCA1A in a patient affected by autosomal dominant cone dystrophy (adCOD), leading to the Asn104His (N104H) amino acid substitution at the protein level. While biochemical analysis of the recombinant protein showed impaired Ca²⁺ sensitivity of the variant, structural properties investigated by circular dichroism and limited proteolysis excluded major structural rearrangements induced by the mutation. Analytical gel filtration profiles and dynamic light scattering were compatible with a dimeric protein both in the presence of Mg²⁺ alone and Mg²⁺ and Ca²⁺. Enzymatic assays showed that N104H-GCAP1 strongly interacts with the GC, with an affinity that doubles that of the WT. The doubled IC₅₀ value of the novel variant (520 nM for N104H vs. 260 nM for the WT) is compatible with a constitutive activity of GC at physiological levels of Ca²⁺. The structural region at the interface with the GC may acquire enhanced flexibility under high Ca²⁺ conditions, as suggested by 2 μs molecular dynamics simulations. The altered interaction with GC would cause hyper-activity of the enzyme at both low and high Ca²⁺ levels, which would ultimately lead to toxic accumulation of cGMP and Ca²⁺ in the photoreceptor outer segment, thus triggering cell death.

Mutations at a split codon in the GTPase-encoding domain of OPA1 cause dominant optic atrophy through different molecular mechanisms

Exonic (i.e. coding) variants in genes associated with disease can exert pathogenic effects both at the protein and mRNA level, either by altering the amino acid sequence or by affecting pre-mRNA splicing. The latter is often neglected due to the lack of RNA analyses in genetic diagnostic testing. In this study we considered both pathomechanisms and performed a comprehensive analysis of nine exonic nucleotide changes in OPA1, which is the major gene underlying autosomal dominant optic atrophy (DOA) and is characterized by pronounced allelic heterogeneity. We focused on the GTPase-encoding domain of OPA1, which harbors most of the missense variants associated with DOA. Given that the consensus splice sites extend into the exons, we chose a split codon, namely codon 438, for our analyses. Variants at this codon are the second most common cause of disease in our large cohort of DOA patients harboring disease-causing variants in OPA1. In silico splice predictions, heterologous splice assays, analysis of patient’s RNA when available, and protein modeling revealed different molecular outcomes for variants at codon 438. The wildtype aspartate residue at amino acid position 438 is directly involved in the dimerization of OPA1 monomers. We found that six amino acid substitutions at codon 438 (i.e. all substitutions of the first and second nucleotide of the codon) destabilized dimerization while only substitutions of the first nucleotide of the codon caused exon skipping. Our study highlights the value of combining RNA analysis and protein modeling approaches to accurately assign patients to future precision therapies.

Impaired Ca2+ Sensitivity of a Novel GCAP1 Variant Causes Cone Dystrophy and Leads to Abnormal Synaptic Transmission Between Photoreceptors and Bipolar Cells

Guanylate cyclase-activating protein 1 (GCAP1) is involved in the shutdown of the phototransduction cascade by regulating the enzymatic activity of retinal guanylate cyclase via a Ca²⁺/cGMP negative feedback. While the phototransduction-associated role of GCAP1 in the photoreceptor outer segment is widely established, its implication in synaptic transmission to downstream neurons remains to be clarified. Here, we present clinical and biochemical data on a novel isolate GCAP1 variant leading to a double amino acid substitution (p.N104K and p.G105R) and associated with cone dystrophy (COD) with an unusual phenotype. Severe alterations of the electroretinogram were observed under both scotopic and photopic conditions, with a negative pattern and abnormally attenuated b-wave component. The biochemical and biophysical analysis of the heterologously expressed N104K-G105R variant corroborated by molecular dynamics simulations highlighted a severely compromised Ca²⁺-sensitivity, accompanied by minor structural and stability alterations. Such differences reflected on the dysregulation of both guanylate cyclase isoforms (RetGC1 and RetGC2), resulting in the constitutive activation of both enzymes at physiological levels of Ca²⁺. As observed with other GCAP1-associated COD, perturbation of the homeostasis of Ca²⁺ and cGMP may lead to the toxic accumulation of second messengers, ultimately triggering cell death. However, the abnormal electroretinogram recorded in this patient also suggested that the dysregulation of the GCAP1–cyclase complex further propagates to the synaptic terminal, thereby altering the ON-pathway related to the b-wave generation. In conclusion, the pathological phenotype may rise from a combination of second messengers’ accumulation and dysfunctional synaptic communication with bipolar cells, whose molecular mechanisms remain to be clarified.

Molecular properties of human guanylate cyclase-activating protein 2 (GCAP2) and its retinal dystrophy-associated variant G157R

In murine and bovine photoreceptors, guanylate cyclase-activating protein 2 (GCAP2) activates retinal guanylate cyclases (GCs) at low Ca²⁺ levels, thus contributing to the Ca²⁺/cGMP negative feedback on the cyclase together with its paralog guanylate cyclase-activating protein 1, which has the same function but different Ca²⁺ sensitivity. In humans, a GCAP2 missense mutation (G157R) has been associated with inherited retinal degeneration (IRD) via an unknown molecular mechanism. Here, we characterized the biochemical properties of human GCAP2 and the G157R variant, focusing on its dimerization and the Ca²⁺/Mg²⁺-binding processes in the presence or absence of N-terminal myristoylation. We found that human GCAP2 and its bovine/murine orthologs significantly differ in terms of oligomeric properties, cation binding, and GC regulation. Myristoylated GCAP2 endothermically binds up to 3 Mg²⁺ with high affinity and forms a compact dimer that may reversibly dissociate in the presence of Ca²⁺. Conversely, nonmyristoylated GCAP2 does not bind Mg²⁺ over the physiological range and remains as a monomer in the absence of Ca²⁺. Both myristoylated and nonmyristoylated GCAP2 bind Ca²⁺ with high affinity. At odds with guanylate cyclase-activating protein 1 and independently of myristoylation, human GCAP2 does not significantly activate retinal GC1 in a Ca²⁺-dependent fashion. The IRD-associated G157R variant is characterized by a partly misfolded, molten globule-like conformation with reduced affinity for cations and prone to form aggregates, likely mediated by hydrophobic interactions. Our findings suggest that GCAP2 might be mostly implicated in processes other than phototransduction in human photoreceptors and suggest a possible molecular mechanism for G157R-associated IRD.

Antibodies elicited by the CaniLeish® vaccine: long-term clinical follow-up study of dogs in Spain

The prevention of canine leishmaniosis in healthy dogs requires a multimodal approach combining repellents with an effective vaccine. A vaccine that modulates the cell-mediated immune response against the protozoan has been available in Europe since 2012 (CaniLeish®, Virbac, France). The aim of the present study was to monitor dogs vaccinated with CaniLeish® to examine the kinetics of the antibody response and the safety and tolerance of CaniLeish®. Dogs vaccinated with CaniLeish® were monitored for 12 months. In follow-up visits at baseline (primovaccination or annual booster) (Visit 1, V1), and 1 (V2), 4 (V3), 8 (V4) and 12 (V5) months later, we examined antibody response kinetics using two serology techniques (IFAT and Speed Leish K™). Tolerance to CaniLeish® and its safety were also monitored. Anti-L. infantum IgG antibodies were determined in 242 dogs (125 dogs after primovaccination (Group P) and 117 dogs after booster vaccination (Group B). In addition, 46, 22 and 19 dogs were followed for 2, 3 and 4 years, respectively. At baseline, 100% of dogs in Group P returned negative IFAT and Speed Leish K™ test results while 9.4% (11/117) in Group B tested IFAT positive though Speed Leish K™ negative. In subsequent visits, seropositivity was detected by IFAT in 31.2% (Group P) and 41% (Group B) of the dogs in V2; 16.8% (Group P) and 10.2% (Group B) in V3; 6.4% (Group P) and 8.5% (Group B) in V4; and 3.2% (Group P) and 5.9% (Group B) in V5. All dogs tested Speed Leish K™ negative except two, in which it was later confirmed by molecular testing that they were not infected. Adverse events that could be associated with the vaccine were detected in 20 out of 314 dogs (6.4%). The good clinical status of all dogs was confirmed in an exhaustive clinical exam and haemato-biochemical profile. The Canileish® vaccine was well-tolerated with exceptions that did not appear to be related to age, sex, race or size of vaccinated dogs. Anti-L. infantum antibodies were detected by IFAT in 31.9-40.3% of the dogs 1 month after vaccination, and these antibodies could still be detected in 3.2% of the dogs 1 year later. This means that veterinarians need to use other tools (eg. PCR) to correctly diagnose seropositive dogs.

Bringing the Ca2+ sensitivity of myristoylated recoverin into the physiological range

The prototypical Ca²⁺-sensor protein recoverin (Rec) is thought to regulate the activity of rhodopsin kinase (GRK1) in photoreceptors by switching from a relaxed (R) disc membrane-bound conformation in the dark to a more compact, cytosol-diffusing tense (T) conformation upon cell illumination. However, the apparent affinity for Ca²⁺ of its physiologically relevant form (myristoylated recoverin) is almost two orders of magnitude too low to support this mechanism in vivo. In this work, we compared the individual and synergistic roles of the myristic moiety, the GRK1 target and the disc membrane in modulating the calcium sensitivity of Rec. We show that the sole presence of the target or the disc membrane alone are not sufficient to achieve a physiological response to changes in intracellular [Ca²⁺]. Instead, the simultaneous presence of GRK1 and membrane allows the T to R transition to occur in a physiological range of [Ca²⁺] with high cooperativity via a conformational selection mechanism that drives the structural transitions of Rec in the presence of multiple ligands. Our conclusions may apply to other sensory transduction systems involving protein complexes and biological membranes.

Modulation of Guanylate Cyclase Activating Protein 1 (GCAP1) Dimeric Assembly by Ca2+ or Mg2+: Hints to Understand Protein Activity

The guanylyl cyclase-activating protein 1, GCAP1, activates or inhibits retinal guanylyl cyclase (retGC) depending on cellular Ca²⁺ concentrations. Several point mutations of GCAP1 have been associated with impaired calcium sensitivity that eventually triggers progressive retinal degeneration. In this work, we demonstrate that the recombinant human protein presents a highly dynamic monomer-dimer equilibrium, whose dissociation constant is influenced by salt concentration and, more importantly, by protein binding to Ca²⁺ or Mg²⁺. Based on small-angle X-ray scattering data, protein-protein docking, and molecular dynamics simulations we propose two novel three-dimensional models of Ca²⁺-bound GCAP1 dimer. The different propensity of human GCAP1 to dimerize suggests structural differences induced by cation binding potentially involved in the regulation of retGC activity.

Aldo-Keto Reductase 1C1 (AKR1C1) as the First Mutated Gene in a Family with Nonsyndromic Primary Lipedema

Lipedema is an often underdiagnosed chronic disorder that affects subcutaneous adipose tissue almost exclusively in women, which leads to disproportionate fat accumulation in the lower and upper body extremities. Common comorbidities include anxiety, depression, and pain. The correlation between mood disorder and subcutaneous fat deposition suggests the involvement of steroids metabolism and neurohormones signaling, however no clear association has been established so far. In this study, we report on a family with three patients affected by sex-limited autosomal dominant nonsyndromic lipedema. They had been screened by whole exome sequencing (WES) which led to the discovery of a missense variant p.(Leu213Gln) in AKR1C1, the gene encoding for an aldo-keto reductase catalyzing the reduction of progesterone to its inactive form, 20-α-hydroxyprogesterone. Comparative molecular dynamics simulations of the wild-type vs. variant enzyme, corroborated by a thorough structural and functional bioinformatic analysis, suggest a partial loss-of-function of the variant. This would result in a slower and less efficient reduction of progesterone to hydroxyprogesterone and an increased subcutaneous fat deposition in variant carriers. Overall, our results suggest that AKR1C1 is the first candidate gene associated with nonsyndromic lipedema.

Missense mutations affecting Ca2+-coordination in GCAP1 lead to cone-rod dystrophies by altering protein structural and functional properties

Guanylate cyclase activating protein 1 (GCAP1) is a neuronal calcium sensor (NCS) involved in the early biochemical steps underlying the phototransduction cascade. By switching from a Ca²⁺-bound form in the dark to a Mg²⁺-bound state following light activation of the cascade, GCAP1 triggers the activation of the retinal guanylate cyclase (GC), thus replenishing the levels of 3',5'-cyclic monophosphate (cGMP) necessary to re-open CNG channels. Here, we investigated the structural and functional effects of three missense mutations in GCAP1 associated with cone-rod dystrophy, which severely perturb the homeostasis of cGMP and Ca²⁺. Substitutions affect residues directly involved in Ca²⁺ coordination in either EF3 (D100G) or EF4 (E155A and E155G) Ca²⁺ binding motifs. We found that all GCAP1 variants form relatively stable dimers showing decreased apparent affinity for Ca²⁺ and blocking the enzyme in a constitutively active state at physiological levels of Ca²⁺. Interestingly, by corroborating spectroscopic experiments with molecular dynamics simulations we show that beside local structural effects, mutation of the bidentate glutamate in an EF-hand calcium binding motif can profoundly perturb the flexibility of the adjacent EF-hand as well, ultimately destabilizing the whole domain. Therefore, while Ca²⁺-binding to GCAP1 per se occurs sequentially, allosteric effects may connect EF hand motifs, which appear to be essential for the integrity of the structural switch mechanism in GCAP1, and perhaps in other NCS proteins.

Neuronal Calcium Sensor GCAP1 Encoded by GUCA1A Exhibits Heterogeneous Functional Properties in Two Cases of Retinitis Pigmentosa

Genetic heterogeneity leading to retinal disorders impairs biological processes by causing, for example, severe disorder of signal transduction in photoreceptor outer segments. A normal balance of the second messenger homeostasis in photoreceptor cells seems to be a crucial factor for healthy and normal photoreceptor function. Genes like GUCY2D coding for guanylate cyclase GC-E and GUCA1A coding for the Ca²⁺-sensor guanylate cyclase-activating protein GCAP1 are critical for a precisely controlled synthesis of the second messenger cGMP. Mutations in GUCA1A frequently correlate in patients with cone dystrophy and cone-rod dystrophy. Here, we report two mutations in the GUCA1A gene that were found in patients diagnosed with retinitis pigmentosa, a phenotype that was rarely detected among previous cases of GUCA1A related retinopathies. One patient was heterozygous for the missense variant c.55C > T (p.H19Y), while the other patient was heterozygous for the missense variant c.479T > G (p.V160G). Using heterologous expression and cell culture systems, we examined the functional and molecular consequences of these point mutations. Both variants showed a dysregulation of guanylate cyclase activity, either a profound shift in Ca²⁺-sensitivity (H19Y) or a nearly complete loss of activating potency (V160G). Functional heterogeneity became also apparent in Ca²⁺/Mg²⁺-binding properties and protein conformational dynamics. A faster progression of retinal dystrophy in the patient carrying the V160G mutation seems to correlate with the more severe impairment of this variant.

New age-related hearing loss candidate genes in humans: an ongoing challenge

Age-related hearing loss (ARHL) is the most frequent sensory disorder in the elderly, affecting approximately one-third of people aged more than 65 years. Despite a large number of people affected, ARHL is still an area of unmet clinical needs, and only a few ARHL susceptibility genes have been detected so far. In order to further investigate the genetics of ARHL, we analyzed a series of 46 ARHL candidate genes, selected according to previous Genome Wide Association Studies (GWAS) data, literature updates and animal models, in a large cohort of 464 Italian ARHL patients. We have filtered the variants according to a) pathogenicity prediction, b) allele frequency in public databases, c) allele frequency in an internal cohort of 113 healthy matched controls, and 81 healthy semi-supercentenarians. After data analysis, all the variants of interest have been tested by functional "in silico" or "in vitro" experiments (i.e., molecular dynamics simulations and protein translation analysis) to assess their pathogenic role, and the expression of the mutated genes have been checked in mouse or zebrafish inner ear. This multi-step approach led to the characterization of a series of ultra-rare likely pathogenic variants in DCLK1, SLC28A3, CEP104, and PCDH20 genes, contributing to describe the first association of these genes with ARHL in humans. These results provide essential insights on the understanding of the molecular bases of such a complex, heterogeneous and frequent disorder, unveiling new possible targets for the future development of innovative therapeutic and preventive approaches that could improve the quality of life of the millions of people affected worldwide.

Oligomeric state, hydrodynamic properties and target recognition of human Calcium and Integrin Binding protein 2 (CIB2)

Calcium- and Integrin-Binding protein 2 (CIB2) is a small and ubiquitously expressed protein with largely unknown biological function but ascertained role in hearing physiology and disease. Recent studies found that CIB2 binds Ca2+ with moderate affinity and dimerizes under conditions mimicking the physiological ones. Here we provided new lines of evidence on CIB2 oligomeric state and the mechanism of interaction with the α7B integrin target. Based on a combination of native mass spectrometry, chemical cross-linking/mass spectrometry, analytical gel filtration, dynamic light scattering and molecular dynamics simulations we conclude that CIB2 is monomeric under all tested conditions and presents uncommon hydrodynamic properties, most likely due to the high content of hydrophobic solvent accessible surface. Surface plasmon resonance shows that the interaction with α7B occurs with relatively low affinity and is limited to the cytosolic region proximal to the membrane, being kinetically favored in the presence of physiological Mg2+ and in the absence of Ca2+. Although CIB2 binds to an α7B peptide in a 1:1 stoichiometry, the formation of the complex might induce binding of another CIB2 molecule.

Effects of Membrane and Biological Target on the Structural and Allosteric Properties of Recoverin: A Computational Approach

Recoverin (Rec) is a prototypical calcium sensor protein primarily expressed in the vertebrate retina. The binding of two Ca²⁺ ions to the functional EF-hand motifs induces the extrusion of a myristoyl group that increases the affinity of Rec for the membrane and leads to the formation of a complex with rhodopsin kinase (GRK1). Here, unbiased all-atom molecular dynamics simulations were performed to monitor the spontaneous insertion of the myristoyl group into a model multicomponent biological membrane for both isolated Rec and for its complex with a peptide from the GRK1 target. It was found that the functional membrane anchoring of the myristoyl group is triggered by persistent electrostatic protein-membrane interactions. In particular, salt bridges between Arg43, Arg46 and polar heads of phosphatidylserine lipids are necessary to enhance the myristoyl hydrophobic packing in the Rec-GRK1 assembly. The long-distance communication between Ca²⁺-binding EF-hands and residues at the interface with GRK1 is significantly influenced by the presence of the membrane, which leads to dramatic changes in the connectivity of amino acids mediating the highest number of persistent interactions (hubs). In conclusion, specific membrane composition and allosteric interactions are both necessary for the correct assembly and dynamics of functional Rec-GRK1 complex.

A novel p.(Glu111Val) missense mutation in GUCA1A associated with cone-rod dystrophy leads to impaired calcium sensing and perturbed second messenger homeostasis in photoreceptors

Guanylate Cyclase-Activating Protein 1 (GCAP1) regulates the enzymatic activity of the photoreceptor guanylate cyclases (GC), leading to inhibition or activation of the cyclic guanosine monophosphate (cGMP) synthesis depending on its Ca2+- or Mg2+-loaded state. By genetically screening a family of patients diagnosed with cone-rod dystrophy, we identified a novel missense mutation with autosomal dominant inheritance pattern (c.332A>T; p.(Glu111Val); E111V from now on) in the GUCA1A gene coding for GCAP1. We performed a thorough biochemical and biophysical investigation of wild type (WT) and E111V human GCAP1 by heterologous expression and purification of the recombinant proteins. The E111V substitution disrupts the coordination of the Ca2+ ion in the high-affinity site (EF-hand 3, EF3), thus significantly decreasing the ability of GCAP1 to sense Ca2+ (∼80-fold higher Kdapp compared to WT). Both WT and E111V GCAP1 form dimers independently on the presence of cations, but the E111V Mg2+-bound form is prone to severe aggregation over time. Molecular dynamics simulations suggest a significantly increased flexibility of both the EF3 and EF4 cation binding loops for the Ca2+-bound form of E111V GCAP1, in line with the decreased affinity for Ca2+. In contrast, a more rigid backbone conformation is observed in the Mg2+-bound state compared to the WT, which results in higher thermal stability. Functional assays confirm that E111V GCAP1 interacts with the target GC with a similar apparent affinity (EC50); however, the mutant shifts the GC inhibition out of the physiological [Ca2+] (IC50E111V ∼10 μM), thereby leading to the aberrant constitutive synthesis of cGMP under conditions of dark-adapted photoreceptors.

Evolutionary-Conserved Allosteric Properties of Three Neuronal Calcium Sensor Proteins

Neuronal Calcium Sensors (NCS) are highly conserved proteins specifically expressed in neurons. Calcium (Ca²⁺)-binding to their EF-hand motifs results in a conformational change, which is crucial for the recognition of a specific target and the downstream biological process. Here we present a comprehensive analysis of the allosteric communication between Ca²⁺-binding sites and the target interfaces of three NCS, namely NCS1, recoverin (Rec), and GCAP1. In particular, Rec was investigated in different Ca²⁺-loading states and in complex with a peptide from the Rhodopsin Kinase (GRK1) while NCS1 was studied in a Ca²⁺-loaded state in complex with either the same GRK1 target or a peptide from the D₂ Dopamine receptor. A Protein Structure Network (PSN) accounting for persistent non-covalent interactions between amino acids was built for each protein state based on exhaustive Molecular Dynamics simulations. Structural network analysis helped unveiling the role of key amino acids in allosteric mechanisms and their evolutionary conservation among homologous proteins. Results for NCS1 highlighted allosteric inter-domain interactions between Ca²⁺-binding motifs and residues involved in target recognition. Robust long range, allosteric protein-target interactions were found also in Rec, in particular originating from the EF3 motif. Interestingly, Tyr 86, involved the hydrophobic packing of the N-terminal domain, was found to be a key residue for both intra- and inter-molecular communication with EF3, regardless of the presence of target or Ca²⁺ ions. Finally, based on a comprehensive topological PSN analysis for Rec, NCS1, and GCAP1 and multiple sequence alignments with homolog proteins, we propose that an evolution-driven correlation may exist between the amino acids mediating the highest number of persistent interactions (high-degree hubs) and their conservation. Such conservation is apparently fundamental for the specific structural dynamics required in signaling events.

Dysfunction of cGMP signalling in photoreceptors by a macular dystrophy-related mutation in the calcium sensor GCAP1

Macular dystrophy leads to progressive loss of central vision and shows symptoms similar to age-related macular degeneration. Genetic screening of patients diagnosed with macular dystrophy disclosed a novel mutation in the GUCA1A gene, namely a c.526C > T substitution leading to the amino acid substitution p.L176F in the guanylate cyclase-activating protein 1 (GCAP1). The same variant was found in three families showing an autosomal dominant mode of inheritance. For a full functional characterization of the L176F mutant we expressed and purified the mutant protein and measured key parameters of its activating properties, its Ca2+/Mg2+-binding, and its Ca2+-induced conformational changes in comparison to the wildtype protein. The mutant was less sensitive to changes in free Ca2+, resulting in a constitutively active form under physiological Ca2+-concentration, showed significantly higher activation rates than the wildtype (90-fold versus 20-fold) and interacted with an higher apparent affinity with its target guanylate cyclase. However, direct Ca2+-binding of the mutant was nearly similar to the wildtype; binding of Mg2+ occurred with higher affinity. We performed molecular dynamics simulations for comparing the Ca2+-saturated inhibiting state of GCAP1 with the Mg2+-bound activating states. The L176F mutant exhibited significantly lower flexibility, when three Ca2+ or two Mg2+ were bound forming probably the structural basis for the modified GCAP1 function.

CaF2 nanoparticles as surface carriers of GCAP1, a calcium sensor protein involved in retinal dystrophies

CaF₂-based nanoparticles (NP) are promising biocompatible tools for nanomedicine applications. The structure of the NP crystal lattice allows for specific interactions with Ca²⁺-binding proteins through their EF-hand cation binding motifs. Here we investigated the interaction of 23 nm citrate-coated CaF₂ NP with a calcium sensor protein GCAP1 that is normally expressed in photoreceptor cells and involved in the regulation of the early steps of vision. Protein-NP interactions were thoroughly investigated for the wild type (WT) GCAP1 as well as for a variant carrying the Asp 100 to Glu mutation (D100E), which prevents the binding of Ca²⁺ to the highest affinity site and is linked to cone dystrophy. Circular dichroism and fluorescence spectroscopy showed that protein structure and Ca²⁺-sensing capability are conserved for both variants upon interaction with the NP surface, although the interaction mode depends on the specific occupation of Ca²⁺-binding sites. NP binding stabilizes the structure of the bound GCAP1 and occurs with nanomolar affinity, as probed by isothermal titration calorimetry. Surface plasmon resonance revealed a fully reversible binding compatible with physiologically relevant kinetics of protein release whereas biochemical assays indicated a residual capability for NP-dissociated GCAP1 to regulate the target retinal guanylate cyclase. Our study constitutes a proof of concept that CaF₂ NP could be optimized to serve as biologically compatible carriers of high amounts of functional GCAP1 in photoreceptors affected by retinal dystrophies.

Flea species infesting dogs in Spain: updated spatial and seasonal distribution patterns

This entomological survey examines the spatial and seasonal distribution patterns of flea species infesting dogs in Spain. Bioclimatic zones covering broad climate and vegetation ranges were surveyed according to size. In a cross-sectional spatial survey carried out from late May 2013 to mid-July 2015, 1084 dogs from 42 different locations were examined. A total of 3032 fleas were collected and identified as belonging to the following species: Ctenocephalides felis (Siphonaptera: Pulicidae) (81.7%, 2476 fleas); Ctenocephalides canis (11.4%, 347 fleas); Pulex irritans (Siphonaptera: Pulicidae) (6.9%, 208 fleas), and Echidnophaga gallinacea (Siphonaptera: Pulicidae) (0.03%, one flea). Variables observed to have effects on flea abundance were animal weight, sex, length of hair and habitat. In the seasonal survey conducted from June 2014 to June 2015, 1014 fleas were collected from 239 dogs at 30 veterinary practices across Spain. Peaks in C. felis abundance were observed in early summer and late autumn, whereas high numbers of P. irritans and C. canis were recorded in autumn. Numbers of fleas detected in winter were low overall. Based on these findings, the present study updates the spatial and seasonal distributions of flea species in Spain and assesses the impacts of host and habitat variables on flea infestation.

The protection of individuals affected with Specific Learning Disorders in the Italian Legislation

Specific Learning Disorders (SLDs) affect specific abilities in individuals with an otherwise normal academic development. Among Italian School population, their reported prevalence is between 2.5% and 3.5%. Dysfunctions at the base of these disorders interfere with the normal acquisition process of reading, writing and/or mathematical abilities, leading to various degrees of adjustment difficulties in the affected individuals. The aim of this study was to assess the support that Italian Government offers to its citizens affected with SLDs, with a particular focus on assistance during the school-age years, particularly through the introduction of the Law 170/2010 and successive guidelines, supplementing the existing regulations to offer more efficient means and legal instruments aimed at achieving earlier diagnoses.

Sleep disorders and driving licence: the current Italian legislation and medico-legal issues

Road traffic accidents (RTA) are a serious issue in all industrialized countries and have dramatic social and healthcare-related implications. Fatigue (sleepiness) is the principal identifiable and preventable cause of road traffic accidents. Obstructive sleep apnoea syndrome (OSAS) and narcolepsy are two of the leading causes of excessive daytime sleepiness. In this article, the authors analyze the current Italian legislation regarding driving licence issuance and fitness to drive, in order to evaluate the potential implications of sleep disorders, particularly OSAS and narcolepsy. In European Legislation and in Italy, OSAS and narcolepsy are not included among the illnesses or invalidating conditions that limit the fitness to drive for driving licence issuance purposes. In fact, they are not included in the Annex III of the European Council Directive 91/439/EEC of the 29th of July 1991 on driving licences. Some Countries of the European Union (Belgium, France, Finland, Great Britain, the Netherlands, Spain and Sweden) had implemented the 91/439/EEC Directive with national restrictions on driving licence issuance policies in case of OSAS and narcolepsy. Given the well-established scientific evidence available, in Italy, the lack of legislation regulating the assessment of the psychophysical requisites for the issuance and renewal of driving licences of individuals affected by sleep disorders seems extremely worrying. Furthermore, the current lack of legal obligation in Italy for healthcare facilities to disclose such diagnoses to the organs responsible for issuing driving licences (such as the Motorizzazione Civile - the Department of motor vehicles) remains the subject of heated debate.

Allosteric communication pathways routed by Ca2+/Mg2+ exchange in GCAP1 selectively switch target regulation modes

GCAP1 is a neuronal calcium sensor protein that regulates the phototransduction cascade in vertebrates by switching between activator and inhibitor of the target guanylate cyclase (GC) in a Ca²⁺-dependent manner. We carried out exhaustive molecular dynamics simulations of GCAP1 and determined the intramolecular communication pathways involved in the specific GC activator/inhibitor switch. The switch was found to depend on the Mg²⁺/Ca²⁺ loading states of the three EF hands and on the way the information is transferred from each EF hand to specific residues at the GCAP1/GC interface. Post-translational myristoylation is fundamental to mediate long range allosteric interactions including the EF2-EF4 coupling and the communication between EF4 and the GC binding interface. Some hubs in the identified protein network are the target of retinal dystrophy mutations, suggesting that the lack of complete inhibition of GC observed in many cases is likely due to the perturbation of intra/intermolecular communication routes.

Biochemical and biophysical characterization of a plant calmodulin: Role of the N- and C-lobes in calcium binding, conformational change, and target interaction

In plants, transient elevation of intracellular Ca(2+) concentration in response to abiotic stress is responsible for glutamate decarboxylase (GAD) activation via association with calmodulin (CaM), an EF-hand protein consisting of two homologous domains (N and C). An unusual 1:2 binding mode of CaM to CaM-binding domains of GAD has long been known, however the contribution of the two CaM domains in target recognition and activation remains to be clarified. Here, we explored the coupling between physicochemical properties of Arabidopsis CaM1 (AtCaM1) and Arabidopsis GAD1 activation, focusing on each AtCaM1 lobe. We found that the four EF-loops of AtCaM1 differently contribute to the ~20 μM apparent affinity for Ca(2+) and the C-lobe shows a ~6-fold higher affinity than N-lobe (Kd(app) 5.6 μM and 32 μM for C- and N-lobes, respectively). AtCaM1 responds structurally to Ca(2+) in a manner similar to vertebrate CaM based on comparison of Ca(2+)-induced changes in hydrophobicity exposure, secondary structure, and hydrodynamic behavior. Molecular dynamics simulations of AtCaM1 apo and Ca(2+)-bound reveal that the latter state is significantly less flexible, although regions of the N-lobe remain quite flexible; this suggests the importance of N-lobe for completing the transition to the extended structure of holoprotein, consistent with data from ANS fluorescence, CD spectroscopy, and SEC analysis. Moreover, enzymatic analysis reveal that mutations in the two lobes affect GAD1 activation in similar ways and only intact AtCaM1 can fully activate GAD1. Taken together, our data provide new insights into the CaM lobes role in interactions between CaM and plant GAD.

Drug outcome survey to evaluate anti-TNF treatment in rheumatoid arthritis: an Italian observational study (the DOSE study)

OBJECTIVES

The aim of this paper is to analyse the use of anti-TNF drugs in current Italian practice, evaluate clinical responses to treatment, and identify possible predictors of negative response in patients with rheumatoid arthritis (RA).

METHODS

DOSE is a non-interventional, prospective study of patients with active RA treated for the first time with anti-TNF agents in 21 Italian hospitals. Demographic and clinical characteristics of patients, treatments and outcome measures were assessed. Outcome measures used were EULAR response, DAS28 remission and HAQ remission at 12 months. A stepwise logistic regression model was used to study the predictors of non-response.

RESULTS

Of 299 RA patients (mean 53.8 ± 12.8 years, 76.1% female), DAS28 was >5.1 in 60.5% of patients and HAQ was >1 in 65.9%. Etanercept was the most prescribed anti-TNF. DMARDs were used in 77.6% of patients (methotrexate in 59.2%). Significant improvements in clinical and laboratory parameters were observed at 12 months. The proportion of patients classed as non-responders remained high, and varied according to assessment criteria. The main predictors independently and significantly associated with a high risk of non-response were: age and female gender for all outcome criteria; high DAS28 value for disease remission; and HAQ >1 for disability remission.

CONCLUSIONS

In Italian anti-TNF treatment for RA, age, gender, and high values of both disease activity and disability were predictors of non-response to first-line therapy with anti-TNF drugs. Future studies should consider optimal second-line therapies for RA patients who do not achieve remission to their first anti-TNF treatment.

Differential Nanosecond Protein Dynamics in Homologous Calcium Sensors

Shaping the temporal response of photoreceptors is facilitated by a well-balanced second messenger cascade, in which two neuronal Ca(2+)-sensor proteins operate in a sequential relay mechanism. Although they share structurally similar sensing units, they differentially activate the same target protein. Here, as a prototypical case in Ca(2+)-mediated signal processing, we investigate differential cellular responsiveness in protein conformational dynamics on a nanosecond time scale. For this, we have site-specifically labeled cysteine residues in guanylate cyclase-activating protein GCAP1 by the fluorescent dye Alexa647 and probed its local environment via time-resolved fluorescence spectroscopy. Fluorescence lifetime and rotational anisotropy measurements reveal a distinct structural movement of the polypeptide chain around position 106 upon release of Ca(2+). This is supported by analyzing the diffusional dye motion in a wobbling-in-a-cone model and by molecular dynamics simulations. We conclude that GCAP1 and its cellular cognate GCAP2 operate by distinctly different switching mechanisms despite their high structural homology.

Two retinal dystrophy-associated missense mutations in GUCA1A with distinct molecular properties result in a similar aberrant regulation of the retinal guanylate cyclase

Two recently identified missense mutations (p. L84F and p. I107T) in GUCA1A, the gene coding for guanylate cyclase (GC)-activating protein 1 (GCAP1), lead to a phenotype ascribable to cone, cone-rod and macular dystrophies. Here, we present a thorough biochemical and biophysical characterization of the mutant proteins and their distinct molecular features. I107T-GCAP1 has nearly wild-type-like protein secondary and tertiary structures, and binds Ca(2+) with a >10-fold lower affinity than the wild-type. On the contrary, L84F-GCAP1 displays altered tertiary structure in both GC-activating and inhibiting states, and a wild type-like apparent affinity for Ca(2+). The latter mutant also shows a significantly high affinity for Mg(2+), which might be important for stabilizing the GC-activating state and inducing a cooperative mechanism for the binding of Ca(2+), so far not been observed in other GCAP1 variants. Moreover, the thermal stability of L84F-GCAP1 is particularly high in the Ca(2+)-bound, GC-inhibiting state. Molecular dynamics simulations suggest that such enhanced stability arises from a deeper burial of the myristoyl moiety within the EF1-EF2 domain. The simulations also support an allosteric mechanism connecting the myristoyl moiety to the highest-affinity Ca(2+) binding site EF3. In spite of their remarkably distinct molecular features, both mutants cause constitutive activation of the target GC at physiological Ca(2+). We conclude that the similar aberrant regulation of the target enzyme results from a similar perturbation of the GCAP1-GC interaction, which may eventually cause dysregulation of both Ca(2+) and cyclic GMP homeostasis and result in retinal degeneration.

Caffeic acid phenethyl ester abrogates bone resorption in a murine calvarial model of polyethylene particle-induced osteolysis

Particle-induced bone loss by osteoclasts is a common cause of aseptic loosening around implants. This study investigates whether caffeic acid phenethyl ester (CAPE), a potent and specific inhibitor of nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 and nuclear factor kappa B, at a low dose reduces bone resorption in a murine calvarial model of polyethylene (PE) particle-induced osteolysis. The effects of particles and CAPE treatment on gastrointestinal tract (GIT) histopathology were also evaluated. Mice were scanned using in vivo animal micro-computed tomography (μCT) as a baseline measurement. PE particles (2.82 × 10(9) particles/mL) were implanted over the calvariae on day 0. CAPE was administered subcutaneously (1 mg/kg/day) at days 0, 4, 7 and 10. Mice were killed at day 14 and serum was analysed for Type-1 carboxyterminal collagen crosslinks (CTX)-1 and osteoclast-associated receptor (OSCAR) levels. Ex vivo μCT scans were conducted to assess bone volume (BV) change and percentage area of calvarial surface resorbed. Calvarial and GIT tissue was processed for histopathology. By day 14, PE particles significantly induced calvarial bone loss compared with control animals as evidenced by resorption areas adjacent to the implanted PE in three-dimensional μCT images, an increase in percentage of resorbed area (p = 0.0022), reduction in BV (p = 0.0012) and increased Tartrate-resistant acid phosphatase positive cells. Serum CTX-1 (p = 0.0495) and OSCAR levels (p = 0.0006) significantly increased in the PE implant group. CAPE significantly inhibited PE particle-induced calvarial osteolysis, as evidenced by a significant reduction in surface bone resorption (p = 0.0012) and volumetric change (p = 0.0154) compared with PE only, but had no effect on systemic CTX-1. Neither particles nor CAPE had an effect on GIT histopathology.

Quantifying not only bone loss, but also soft tissue swelling, in a murine inflammatory arthritis model using micro-computed tomography

In rodent models of inflammatory arthritis, bone erosion has been non-invasively assessed by micro-computed tomography (micro-CT). However, non-invasive assessments of paw swelling (oedema) are still based on clinical grading by visual evaluation, or measurements by callipers, not always reliable for the tiny mouse paws. The aim of this work was to demonstrate a novel straightforward 3D micro-CT analysis protocol capable of quantifying not only joint bone erosion, but also soft tissue swelling, from the same scans, in a rodent inflammatory arthritis model. Balb/c mice were divided into two groups: collagen antibody-induced arthritis (CAIA) and CAIA treated with prednisolone, the latter reflecting an established treatment in human rheumatoid arthritis. Clinical paw scores were recorded. On day 10, front paws were assessed by micro-CT and histology. Micro-CT measurements included paw volume (bone and soft tissue together) and bone volume at the radiocarpal joint, and bone volume from the radiocarpal to the metacarpophalangeal joint. Micro-CT analysis revealed significantly lower paw volume (−36%, P < 0.01) and higher bone volume (+17%, P < 0.05) in prednisolone-treated CAIA mice compared with untreated CAIA mice. Paw volume and bone volume assessed by micro-CT correlated significantly with clinical and histological scores (|r| > 0.5, P < 0.01). Untreated CAIA mice showed significantly higher clinical scores, higher inflammation levels histologically, cartilage and bone degradation, and pannus formation, compared with treated mice (P < 0.01). The presented novel micro-CT analysis protocol enables 3D-quantification of paw swelling at the micrometre level, along with the typically assessed bone erosion, using the same images/scans, without altering the scanning procedure or using contrast agents.

Structural plasticity of calmodulin on the surface of CaF2 nanoparticles preserves its biological function

Nanoparticles are increasingly used in biomedical applications and are especially attractive as biocompatible and biodegradable protein delivery systems. Herein, the interaction between biocompatible 25 nm CaF2 nanoparticles and the ubiquitous calcium sensor calmodulin has been investigated in order to assess the potential of these particles to serve as suitable surface protein carriers. Calmodulin is a multifunctional messenger protein that activates a wide variety of signaling pathways in eukaryotic cells by changing its conformation in a calcium-dependent manner. Isothermal titration calorimetry and circular dichroism studies have shown that the interaction between calmodulin and CaF2 nanoparticles occurs with physiologically relevant affinity and that the binding process is fully reversible, occurring without significant alterations in protein secondary and tertiary structures. Experiments performed with a mutant form of calmodulin having an impaired Ca(2+)-binding ability in the C-terminal lobe suggest that the EF-hand Ca(2+)-binding motifs are directly involved in the binding of calmodulin to the CaF2 matrix. The residual capability of nanoparticle-bound calmodulin to function as a calcium sensor protein, binding to and altering the activity of a target protein, was successfully probed by biochemical assays. Even if efficiently carried by CaF2 nanoparticles, calmodulin may dissociate, thus retaining the ability to bind the peptide encompassing the putative C-terminal calmodulin-binding domain of glutamate decarboxylase and activate the enzyme. We conclude that the high flexibility and structural plasticity of calmodulin are responsible for the preservation of its function when bound in high amounts to a nanoparticle surface.

Pruritus and quality of life in moderate-to-severe plaque psoriasis: post hoc explorative analysis from the PRISTINE study

BACKGROUND

Pruritus is a clinically important symptom of psoriasis that has a major impact on quality of life (QoL).

OBJECTIVE

The objective of this study was to examine pruritus and QoL in patients with moderate-to-severe psoriasis treated with etanercept (ETN) in the PRISTINE clinical trial.

METHODS

Patients were randomized (1 : 1, double-blind) to ETN 50 mg QW or 50 mg BIW for 12 weeks, followed by 50 mg QW for 12 weeks. Pruritus was reported as 0 (no itching) to 5 (severe itching). Associations were examined between pruritus and Psoriasis Area and Severity Index, Dermatology Life Quality Index (DLQI), Hospital Anxiety and Depression Screening (HADS), Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue), Euro-Qol 5D (EQ-5D) and Medical Outcomes Study (MOS) Sleep Index II.

RESULTS

At baseline, patients (n = 270) had a mean pruritus level of 3.6. Itching (level ≥1) was reported by 96% of patients, 62% of whom had severe itching (level ≥4) and 26% had the highest level of itching. DLQI, HADS-Anxiety, HADS-Depression, FACIT-Fatigue, EQ-5D visual analog scale, and MOS Sleep Index II were significantly associated with itch. At week 12, mean pruritus improvement in the ETN BIW/QW group was greater than in the QW/QW group (2.4 vs. 1.6, P < 0.001), but not at week 24 (2.2 vs. 2.0, P = 0.180). Patients with the most severe itching at baseline (score of 5) had a mean score of 1.7 at week 24. Overall, patients with clinically meaningful pruritus improvement at week 24 reported greater improvement in QoL measures than other patients.

CONCLUSION

Most patients with moderate-to-severe psoriasis in this study (96%) reported pruritus. Pruritus improved significantly with ETN therapy and was strongly associated with improvements in QoL. These data support the clinical relevance of pruritus as an important symptom of patients with moderate/severe psoriasis.

Structural effects of Mg²⁺ on the regulatory states of three neuronal calcium sensors operating in vertebrate phototransduction

The effects of physiological concentration of magnesium on the switch states of the neuronal calcium sensor proteins recoverin, GCAP1 and GCAP2 were investigated. Isothermal titration calorimetry was applied for binding studies. Circular dichroism spectroscopy was used to characterize protein thermal stability, secondary and tertiary structure in conditions of high and low [Ca²⁺], mimicking respectively the dark-adapted and light-exposed photoreceptor states during the phototransduction cascade. Further, molecular dynamics (MD) simulations were run to investigate the dynamical structural properties of GCAP1 in its activator, inhibitor and putative transitory states. Our results confirmed that Mg²⁺ is unable to trigger the typical Ca²⁺-induced conformational change of recoverin (myristoyl switch) while it decreases its thermal stability. Interestingly, Mg²⁺ seems to affect the conformation of GCAP2 both at high and low [Ca²⁺], however the variations are more substantial for myristoylated GCAP2 in the absence of Ca²⁺. GCAP1 is responsive to Mg²⁺ only in its low [Ca²⁺] state and Mg²⁺-GCAP1 tertiary structure slightly differs from both apo and Ca²⁺-bound states. Finally, MD simulations suggest that the GCAP1 state harboring one Mg²⁺ ion bound to EF2 acquires structural characteristics that are thought to be relevant for the activation of the guanylate cyclase. Moreover, all the putative Mg²⁺-bound states of myristoylated GCAP1 are structurally less flexible than Ca²⁺-bound states. GCAP1 acquires a more compact tertiary structure that is less accessible to the solvent, thereby inducing a different conformation to the myristoyl moiety, which might be crucial for the activation of the guanylate cyclase. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

Surface scratch assessment of titanium implant abutments and cementum following instrumentation with metal curettes

OBJECTIVES

This study was conducted to compare the surface scratch resistance of titanium implant abutments and cementum to evaluate the impact of scaling with metal curettes on both surfaces.

MATERIALS AND METHODS

A standard in vitro force of 14 N was used to assess the scratch width and depth created by curettes on extracted human tooth roots and titanium implant abutments. Scratch width and depth were analysed using a stereomicroscope and non-contact surface profilometry.

RESULTS

The mean force applied during test scaling procedures by experienced volunteer operators was 14 N. Mechanical scaling using this force in vitro of cementum produced a mean scratch width of 59.4 ± 1.9 μm, N = 20, and scratch depth of 0.86 ± 0.03 μm, N = 20, compared to the titanium abutments' mean scratch width of 30.8 ± 1.9 μm, N = 6, and scratch depth of 0.34 ± 0.02 μm, N = 6. These differences were statistically significant (P < 0.05).

CONCLUSIONS

Although there a number of factors in the clinical situation which are not easily reproducible in vitro, this proof-of-principle in vitro study is the first to confirm quantitatively that titanium abutments had a significantly greater scratch resistance than cementum when metal curettes were used on these surfaces. This information should be considered, especially if there is a preferred choice of metal instruments for effective dental prophylactic procedures for the maintenance of titanium dental implants.

CLINICAL RELEVANCE

Clinical dogma suggests that titanium implant abutment surfaces should not be instrumented with metal instruments due to scratching of the surface. However, since cementum is softer than titanium, the logic of this tenet seems flawed. This study demonstrated for the first time that titanium abutments undergo less scratch damage during scaling with metal curettes than does cementum. Metal curettes may be used on titanium abutments with as much confidence as for root planing on natural teeth.

Impact of cone dystrophy-related mutations in GCAP1 on a kinetic model of phototransduction

Cone dystrophy-related mutations in guanylate cyclase-activating protein 1 (GCAP1) are known to cause severe disturbance of their Ca(2+)-sensing properties affecting also their regulatory modes. However, crucial biochemical properties of mutant GCAP1 forms have not been fully elucidated and regulatory parameters of GCAP1 mutants have not been considered within the context of a comprehensive description of the phototransduction cascade kinetics. We investigated therefore the structure-function relationships of four dystrophy-relevant point mutations in GCAP1 harboring the following amino acid substitutions: E89K, D100E, L151F, and G159V. All mutations decrease the catalytic efficiency in regulating the target guanylate cyclase and decrease the affinity of Ca(2+)-binding in at least one, but in most cases two EF-hand Ca(2+)-binding sites. Although the wild type and mutants of GCAP1 displayed large differences in Ca(2+)-binding and regulation, circular dichroism (CD) spectroscopy revealed that all proteins preserved an intact secondary and tertiary structure with a significant rearrangement of the aromatic residues upon binding of Ca(2+). To gain insight into the dynamic changes of cyclic GMP levels in a photoreceptor cell, we incorporated parameters describing the regulation of target guanylate cyclase by GCAP1 mutants into a comprehensive kinetic model of phototransduction. Modeling led us to conclude that the contribution of GCAP1 to the dynamic synthesis of cyclic GMP in rod cells would depend on the expression level of the wild-type form. Although the synthesis rate controlled by GCAP1 remains at a constant level, in the case of high expression levels of cone-dystrophy GCAP1 mutants it would not contribute at all to shaping the cGMP rate, which becomes dynamically regulated solely by the other present Ca(2+)-sensor GCAP2.

Nanodevice-induced conformational and functional changes in a prototypical calcium sensor protein

Calcium (Ca(2+)) plays a major role in a variety of cellular processes. Fine changes in its concentration are detected by calcium sensor proteins, which adopt specific conformations to regulate their molecular targets. Here, two distinct nanodevices were probed as biocompatible carriers of Ca(2+)-sensors and the structural and functional effects of protein-nanodevice interactions were investigated. The prototypical Ca(2+)-sensor recoverin (Rec) was incubated with 20-25 nm CaF2 nanoparticles (NPs) and 70-80 nm liposomes with lipid composition similar to that found in photoreceptor cells. Circular dichroism and fluorescence spectroscopy were used to characterize changes in the protein secondary and tertiary structure and in thermal stability upon interaction with the nanodevice, both in the presence and in the absence of free Ca(2+). Variations in the hydrodynamic diameter of the complex were measured by dynamic light scattering and the residual capability of the protein to act as a Ca(2+)-sensor in the presence of NPs was estimated spectroscopically. The conformation, thermal stability and Ca(2+)-sensing capability of Rec were all significantly affected by the presence of NPs, while liposomes did not significantly perturb Rec conformation and function, allowing reversible binding. NP-bound Rec maintained an all-helical fold but showed lower thermal stability and high cooperativity of unfolding. Our analysis can be proficiently used to validate the biocompatibility of other nanodevices intended for biomedical applications involving Ca(2+)-sensors.