Clinical and pathologic differences in interstitial lung disease based on antisynthetase antibody type

BACKGROUND

Interstitial lung disease (ILD) is a common extramuscular manifestation of the idiopathic inflammatory myopathies (IIMs), dermatomyositis (DM) and polymyositis (PM). Patients with antisynthetase antibodies (ASA) demonstrate some or all of the features of the antisynthetase syndrome including IIM and ILD. It has been hypothesized that the clinical expression of antisynthetase syndrome varies between specific ASAs.

OBJECTIVE

We sought to determine whether the myositis-associated ILD (MA-ILD) phenotype differs based on the presence of ASAs and by ASA subtype.

METHODS

A cross-sectional and longitudinal analysis of consecutive patients enrolled at the Johns Hopkins Myositis Center with ILD in the setting of clinically diagnosed autoimmune myositis was conducted.

RESULTS

Seventy-seven subjects were included; 36 were ASA negative, 28 were anti-Jo1 positive, and 13 were non-Jo1 ASA positive (5 anti-PL-12, 4 anti-PL-7, 2 anti-EJ, and 2 anti-OJ). Non-Jo1 ASA positive participants were more likely to be African-American than Caucasian as compared to both the anti-Jo1 positive (p = 0.01) and ASA negative groups (p < 0.01). ASA negative participants had better mean forced vital capacity percent predicted (FVC%) and total computed tomography scores over time compared to those with anti-Jo1 after controlling for potential confounders.

CONCLUSIONS

ASA status was significantly different by race. Those with anti-Jo1 antibodies had worse lung function and CT scores over time compared to those without detectable antisynthetase antibodies. Further prospective study in a larger cohort is needed to determine whether these apparent antibody-specific differences in demographics and manifestations of disease translate into meaningful disparities in clinical outcomes.

TFII-I, a candidate gene for Williams syndrome cognitive profile: parallels between regional expression in mouse brain and human phenotype

The gene for TFII-I, a widely expressed transcription factor, has been localized to an interval of human chromosome 7q11.23 that is commonly deleted in Williams syndrome (WS). The clinical phenotype of WS includes elfin facies, infantile hypercalcemia, supravalvular aortic stenosis, hyperacusis and mental retardation. The WS cognitive profile (WSCP) is notable for the differential impairment of visual-spatial abilities with relative sparing of verbal-linguistic function. Fine mapping of individuals with WS has revealed a close association between deletion of TFII-I and the WSCP. To determine the plausibility of the hypothesis that hemizygous deletion of TFII-I contributes to the WSCP, we have examined the anatomic distribution of TFII-I RNA and protein isoforms in brains from adult and embryonic mice. Our studies show that early in development, TFII-I expression is widespread and nearly uniform throughout the brain. In adult brain, TFII-I protein is present exclusively in neurons. Highest levels of expression are observed in cerebellar Purkinje cells and in hippocampal interneurons. TFII-I immunoreactivity is distinct from that of the related protein, TFII-IRD1, which is also localized to the region of human chromosome 7 deleted in WS. The expression pattern of TFII-I in mouse brain parallels regions in human brain which have been shown to be anatomically and functionally altered in humans with WS. These observations are consistent with the hypothesis that deletion of the gene for TFII-I contributes to the cognitive impairments observed in WS.

Pleuropulmonary disease due to pergolide use for restless legs syndrome

Pergolide is an ergot-derived dopamine agonist used in Parkinson's disease and, increasingly, in restless legs syndrome. We report a patient with a 2.5-year history of weight loss, pleuropulmonary fibrosis, and exudative pleural effusion that developed insidiously while taking this medication. The extensive and invasive workup that preceded the diagnosis highlights the difficulty in attributing such a process to a drug reaction. This is the second report of such a reaction to pergolide, which is one of the increasing number of ergot-derived compounds in common clinical use.

The inositol trisphosphate receptor gene family: implications for normal and abnormal brain function

1. The phosphatidyl inositol (PI) second messenger system has been extensively investigated in the past decade. This complex pathway results in the production of two second messengers, one of which, inositol 1,4,5-trisphosphate, will be the focus of this review. 2. The intracellular receptor for this second messenger (IP3R) has been purified, reconstituted and extensively characterized in both brain and peripheral tissues. 3. Localization and functional studies show that IP3 binding causes the receptor to release portions of the intracellular calcium stores. 4. Multiple modulators of the receptor have been identified, including pH, calcium concentration, adenine nucleotide concentration and phosphorylation. 5. The cDNA for this molecule has been cloned from a number of sources. Studies of the molecular structure of the receptor have revealed additional levels of complexity including multiple alternative splicing events in the initially cloned cerebellar (Type I) receptor, as well as the existence of highly related but distinct cDNAs which likely reflect a gene family. 6. There is suggestive evidence linking the PI system, and thus the IP3R, to bipolar disorder and the actions of lithium.

Inositol (1,4,5)-trisphosphate receptor: characterization of neuron-specific alternative splicing in rat brain and peripheral tissues

One source of diversity in the inositol (1,4,5)-trisphosphate receptors (IP3Rs) is generated at the level of alternative splicing. Our previous studies of splice isoforms of the receptor in various tissues suggested that some tissues, specifically those containing neurons, selectively express a 40 amino acid insert located between 2 sites for phosphorylation by cyclic AMP-dependent protein kinase (PKA), and that the presence of this insert changes the preferred site of phosphorylation of the receptor. Studies of the mouse receptor have also suggested the existence of intermediately spliced forms containing partial versions of the splice and exhibiting different brain distributions. In this study, we have investigated the alternative splicing of the rat receptor in greater detail using RNase protection and PCR analysis. We find little evidence for the existence of intermediately spliced forms in rat, raising the possibility that the degree of alternative splicing at this site differs in the brains of two very similar species. Our screen of tissue distribution supports the selectively neuronal expression of the long spliced form, and suggests that regulation of this receptor in neurons may be different than in other tissues.

Three additional inositol 1,4,5-trisphosphate receptors: molecular cloning and differential localization in brain and peripheral tissues

Three inositol 1,4,5-trisphosphate receptor (IP3R) cDNAs, designated IP3R-II, -III, and -IV, were cloned from a mouse placenta cDNA library. All three display strong homology in membrane-spanning domains M7 and M8 to the originally cloned cerebellar IP3R-I, with divergences predominantly in cytoplasmic domains. Levels of mRNA for the three additional IP3Rs in general are substantially lower than for IP3R-I, though in the gastrointestinal tract the levels of IP3R-III may be comparable to IP3R-I. Cerebellar Purkinje cells express at least two and possibly three distinct IP3Rs, suggesting heterogeneity of IP3 action within a single cell.

Inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate receptor proteins: isolation and characterization from rat brain

High-affinity, membrane-associated inositol 1,3,4,5-tetrakisphosphate (IP4) and inositol hexakisphosphate (IP6) binding proteins were solubilized and isolated utilizing a heparin-agarose resin followed by an IP4 affinity resin. The IP6 receptor comprises a protein complex of 115-, 105-, and 50-kDa subunits, all of which comigrate under native conditions. The Kd of the receptor for IP6 is 12 nM, whereas inositol 1,3,4,5,6-pentakisphosphate (IP5), IP4, and inositol 1,4,5-trisphosphate (IP3) are 50%, 30%, and 15%, respectively, as potent. Two protein complexes copurify with the IP4 receptor fraction. A 182/123-kDa complex elutes first from the affinity column followed by a 174/84-kDa protein complex, which elutes at higher salt. Both complexes show high affinity for IP4 (Kd = 3-4 nM). IP5, IP6, and IP3 display approximately 25%, 10%, and 0.1%, respectively, the affinity of IP4. Ligand binding to IP6 and IP4 receptors is inhibited 50% by heparin at 0.1 microgram/ml. IP4 receptor proteins are stoichiometrically phosphorylated by cyclic AMP-dependent protein kinase and protein kinase C, whereas negligible phosphorylation is observed for the IP6 receptor.

Inositol 1,4,5-trisphosphate receptors: distinct neuronal and nonneuronal forms derived by alternative splicing differ in phosphorylation

We have identified two distinct transcripts of inositol 1,4,5-trisphosphate receptor by using the PCR on first-strand cDNAs from various rat tissues. The longer form, corresponding to the previously cloned adult rat brain inositol 1,4,5-trisphosphate receptor, contains a 120-nucleotide insert between the two cAMP-dependent protein kinase phosphorylation consensus sequences. The shorter form (lacking the insert) predominates in fetal brain and peripheral tissues and appears to represent a nonneuronal receptor, whereas the longer form is found in adult brain and appears to be exclusively neuronal. The phosphorylation kinetics by cAMP-dependent protein kinase and the phosphopeptide maps differ for inositol 1,4,5-trisphosphate receptors purified from tissues predominantly expressing different forms of the transcript.

Solubilization and separation of inositol 1,3,4,5-tetrakisphosphate- and inositol 1,4,5-trisphosphate-binding proteins and metabolizing enzymes in rat brain

The two inositol phosphate-binding proteins, the Ins(1,4,5)P3 (InsP3) and Ins(1,3,4,5)P4 (InsP4) receptors, and the two particulate InsP3-metabolizing enzymes, InsP3 5-phosphatase and InsP3 3-kinase, were solubilized with detergent from rat cerebellar membranes. These four activities are shown to be distinct molecular species by separation using a variety of protein chromatographic steps. The pharmacology of the partially purified InsP4-binding site indicates that the binding has a high affinity and selectivity for InsP4 over InsP3. These results suggest the existence of a distinct specific InsP4-binding protein which may represent the receptor for this putative second messenger.

Cyclic AMP-dependent phosphorylation of a brain inositol trisphosphate receptor decreases its release of calcium

We report the stoichiometric phosphorylation of an inositol 1,4,5-trisphosphate receptor-binding protein from rat brain by the cAMP-dependent protein kinase but not by protein kinase C or Ca2+/calmodulin-dependent protein kinase. This phosphorylation event does not markedly alter [3H]inositol 1,4,5-trisphosphate-binding characteristics. However, inositol 1,4,5-trisphosphate is only 10% as potent in releasing 45Ca2+ from phosphorylated, as compared with native, cerebellar microsomes. Phosphorylation of the inositol 1,4,5-trisphosphate-binding protein by the cAMP-dependent protein kinase may provide a biochemical substrate for second-messenger cross talk.

Characterization of a membrane protein from brain mediating the inhibition of inositol 1,4,5-trisphosphate receptor binding by calcium

Inositol 1,4,5-trisphosphate (InsP3) is a component of the phosphoinositide second-messenger system which mobilizes Ca2+ from intracellular stores. Recently, an InsP3 receptor binding protein from rat cerebellar membranes was solubilized and purified to homogeneity. The potent inhibition by Ca2+ of [3H]InsP3 binding to the InsP3 receptor in cellular membranes is not apparent in the purified receptor. The Ca2+-dependent inhibition of [3H]InsP3 binding in the crude homogenate (concn. giving 50% inhibition = 300 nM) can be restored by addition of solubilized cerebellar membranes to the purified receptor. In the present study, we further characterize the protein in solubilized membranes which confers Ca2+-sensitivity to the receptor, and which we term 'calmedin'. Calmedin appears to be a neutral membrane protein with an estimated Mr of 300,000 by gel filtration in the presence of Triton X-100. Calmedin confers a Ca2+-sensitivity to InsP3 receptor binding, which can be completely reversed by 10 min incubation with EDTA and therefore does not represent Ca2+-dependent proteinase action. Calmedin effects on the purified InsP3 receptor depend on Ca2+ binding to the calmedin, although Ca2+ also binds directly to the InsP3 receptor. The regional distribution of calmedin differs from that of the InsP3 receptor in the brain, suggesting that it also mediates other Ca2+-dependent functions. Calmedin activity in peripheral tissues is much lower than in brain.