Anti-N-methyl-D-aspartate receptor and anti-ribosomal-P autoantibodies contribute to cognitive dysfunction in systemic lupus erythematosus.

OBJECTIVE: Autoantibodies against N-methyl-D-aspartate receptor (anti-NMDAR) and ribosomal-P (anti-P) antigens are potential pathogenic factors in the frequently observed diffuse brain dysfunctions in patients with systemic lupus erythematosus (SLE). Although studies have been conducted in this area, the role of anti-NMDAR antibodies in SLE cognitive dysfunction remains elusive. Moreover, the specific contribution of anti-P antibodies has not been reported yet. The present study attempts to clarify the contribution of anti-NMDAR and anti-P antibodies to cognitive dysfunction in SLE. METHODS: The Cambridge Neuropsychological Test Automated Battery (CANTAB) was used to assess a wide range of cognitive function areas in 133 Chilean women with SLE. ANCOVA models included autoantibodies, patient and disease features. RESULTS: Cognitive deficit was found in 20%. Higher SLEDAI-2K scores were associated with impairment in spatial memory and learning abilities, whereas both anti-NMDAR and anti-P antibodies contributed to deficits in attention and spatial planning abilities, which reflect fronto-parietal cortex dysfunctions. CONCLUSIONS: These results reveal an association of active disease together with specific circulating autoantibodies, such as anti-NMDAR and anti-P, with cognitive dysfunction in SLE patients.

Systemic lupus erythematosus impairs memory cognitive tests not affected by depression.

OBJECTIVE: Our aim was to assess the contribution of depression to cognitive impairment in patients with systemic lupus erythematosus (SLE). METHODS: Clinical features, education, age, and Hospital Anxiety and Depression Scale (HADS) were evaluated in 82 patients with SLE and 22 healthy controls, all Chilean women. The Cambridge Neuropsychological Test Automated Battery (CANTAB eclipseTM) assessing attention, spatial memory, and learning and executive function domains was applied. Cognitive deficit definition: a cut-off for definite impairment was defined as a score below -2 standard deviations in at least one outcome measure in two or more domains. ANCOVA with stepwise selection evaluated influences of health status (SLE or control), age, education, and HADS depression and anxiety scores on cognitive outcomes. To avoid overfitting, a shrinkage method was performed. Also, adjusted p-values for multiple comparisons were obtained. RESULTS: Cognitive deficit affected 16 (20%) patients, and no controls (p=0.039). Median HADS depression score in SLE patients was 6 (range 0-19) and in controls was 0 (0-19), p<0.001). ANCOVA and shrinkage models showed that worse cognitive performance in sustained attention and spatial working memory tests was explained by the presence of SLE but not depression, whereas depression only affected a measure of executive function (I/ED Stages completed). CONCLUSION: Depression has a limited role in cognitive impairment in SLE. Impairments in sustained attention and spatial working memory are distinctly influenced by yet-unknown disease-intrinsic factors.

Common mental disorders and psychological distress in systemic lupus erythematosus are not associated with disease activity.

Psychiatric diagnosis in patients with systemic lupus erythematosus (SLE) is controversial: variations have been reported in frequency, diagnostic assays, associations with disease activity, autoantibodies, and contributing social factors. Eighty-three consecutive non-selected Chilean patients with SLE were evaluated for: (i) 26 common mental disorders according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), using the Mini-International Neuropsychiatric Interview (MINI-plus); (ii) psychological suffering measured by Hospital Anxiety and Depression Scale (HADS); (iii) ACR 1999 neuropsychiatric (NP)SLE criteria; (iv) SLE disease activity (SLEDAI-2K); (v) cumulative damage (SLICC/ACR); and (vi) anti-ribosomal P antibodies by enzyme-linked immunoassay and immunoblot. Psychiatric diagnoses occurred in 44.6% of patients; the most frequent (21.7%) was major depressive episode (MDE). No association with lupus activity was observed in patients with a DSM-IV diagnosis or MDE or psychological suffering. ACR 1999 NPSLE criteria were present in 42.2% of patients, the majority corresponding to mood (28.9%) or anxiety disorders (15.6%). Suicidal risk was present in 9.6% of patients. Anti-ribosomal P antibodies (13.3%) were not associated with DSM-IV diagnosis. Severe psychiatric disorders in SLE are common and not associated with disease activity.

Apical sorting of a voltage- and Ca2+-activated K+ channel alpha -subunit in Madin-Darby canine kidney cells is independent of N-glycosylation.

The voltage- and Ca(2+)-activated K(+) (K(V,Ca)) channel is expressed in a variety of polarized epithelial cells seemingly displaying a tissue-dependent apical-to-basolateral regionalization, as revealed by electrophysiology. Using domain-specific biotinylation and immunofluorescence we show that the human channel K(V,Ca) alpha-subunit (human Slowpoke channel, hSlo) is predominantly found in the apical plasma membrane domain of permanently transfected Madin-Darby canine kidney cells. Both the wild-type and a mutant hSlo protein lacking its only potential N-glycosylation site were efficiently transported to the cell surface and concentrated in the apical domain even when they were overexpressed to levels 200- to 300-fold higher than the density of intrinsic Slo channels. Furthermore, tunicamycin treatment did not prevent apical segregation of hSlo, indicating that endogenous glycosylated proteins (e.g., K(V,Ca) beta-subunits) were not required. hSlo seems to display properties for lipid-raft targeting, as judged by its buoyant distribution in sucrose gradients after extraction with either detergent or sodium carbonate. The evidence indicates that the hSlo protein possesses intrinsic information for transport to the apical cell surface through a mechanism that may involve association with lipid rafts and that is independent of glycosylation of the channel itself or an associated protein. Thus, this particular polytopic model protein shows that glycosylation-independent apical pathways exist for endogenous membrane proteins in Madin-Darby canine kidney cells.

Sarcomeric myosin heavy chain expressed in nonmuscle cells forms thick filaments in the presence of substoichiometric amounts of light chains.

Central to the function of myosin is its ability to assemble into thick filaments which interact precisely and specifically with other myofibrillar proteins. We have established a novel experimental system for studying myofibrillogenesis using transient transfections of COS cells, a monkey kidney cell line. We have expressed both full-length rat alpha cardiac myosin heavy chain (MHC) and a truncated heavy meromyosin-like alpha MHC (sHMM) and shown that immunoreactive MHC proteins of the expected sizes were detected in lysates of transfected cells. Surprisingly, the full-length MHC formed large spindle-shaped structures throughout the cytoplasm of transfected cells as determined by immunofluorescence microscopy. The structures were not found in cells expressing the sHMM construct, indicating that their formation required an MHC rod. The spindle-shaped structures ranged in length from approximately 1 micron to over 20 microns in length and were birefringent suggesting that they are ordered arrays of thick filaments. This was confirmed by electron microscopic analysis of the transfected cells which revealed arrays of filamentous structures approximately 12 nm in diameter at their widest point. In addition, the vast majority of transfected MHC did not associate with the endogenous nonmuscle myosin light chains, demonstrating that myosin thick filaments can form in the absence of stoichiometric amounts of myosin light chains.

Identification of sequences necessary for the association of cardiac myosin subunits.

To begin to understand the nature of myosin subunit assembly, we determined the region of a vertebrate sarcomeric myosin heavy chain required for binding of light chain 1. We coexpressed in Escherichia coli segments of the rat alpha cardiac myosin heavy chain which spanned the carboxyl terminus of subfragment 1 and the amino terminus of subfragment 2 with a full-length rat cardiac myosin light chain 1. A 16 amino acid region of the myosin heavy chain (residues 792-808) was shown to be required for myosin light chain 1 binding in an immunoprecipitation assay.

Full-length rat alpha and beta cardiac myosin heavy chain sequences. Comparisons suggest a molecular basis for functional differences.

The two cardiac myosin heavy chain isoforms, alpha and beta, differ functionally, alpha Myosin exhibits higher actin-activated ATPase than does beta myosin, and hearts expressing alpha myosin exhibit increased contractility relative to hearts expressing beta myosin. To understand the molecular basis for this functional difference, we determined the complete nucleotide sequence of full-length rat alpha and beta myosin heavy chain cDNAs. This study represents the first opportunity to compare full-length fast ATPase and slow ATPase muscle myosin sequences. The alpha and beta myosin heavy chain amino acid sequences are more related to each other than to other sarcomeric myosin heavy chain sequences. Of the 1938 amino acid residues in alpha and beta myosin heavy chain, 131 are non-identical with 37 non-conservative changes. Two-thirds of these non-identical residues are clustered, and several of these clusters map to regions that have been implicated as functionally important. Some of the regions identified by the clusters of non-identical amino acid residues may affect actin binding, ATP hydrolysis and force production.