Immunolocalization of cystinosin,the protein defective in cystinosis

Cystinosis is an autosomal recessive disorder associated with excessive lysosomal cystine accumulation secondary to defective lysosomal cystine efflux. CTNS, the gene mutated in cystinosis, codes for the lysosomal membrane protein cystinosin. Antisera were raised in rabbits to a carboxy-terminal oligopeptide sequence from cystinosin. Antisera were screened by Western blotting and immunocytochemical analyses of transfected COS-7 cells expressing either human wild-type cystinosin, a wild-type cystinosin-green fluorescent protein (GFP) fusion protein, or a fusion protein of GFP and mutant human cystinosin with a carboxy-terminal deletion. In Western blots, bands corresponding to cystinosin or cystinosin-GFP were observed in transfected cells but no signal was detected in cells expressing the carboxy-terminal mutant; preimmune sera yielded negative results in all three cases. In transfected cells expressing wild-type cystinosin, immunoreactivity appeared in subcellular vesicles. In cells expressing the wild-type cystinosin-GFP fusion protein, immunoreactivity colocalized with GFP fluorescence. Previous studies demonstrated that GFP fluorescence from this construct colocalized with immunostaining for a known lysosomal membrane protein, i.e., lysosome-associated membrane protein 2. In immunohistochemical analyses, cystinosin localized to tubule epithelia in three normal human kidneys, with a pattern similar to that of lysosome-associated membrane protein 2; cystinosin immunoreactivity was absent in kidneys from patients with a CTNS deletion. For the first time, antisera have been raised that localize cystinosin in cells in vitro and in vivo.     

A processive versus a distributive mechanism of action correlates with differences in ability of normal and xeroderma pigmentosum group A endonucleases to incise damaged nucleosomal DNA

A DNA endonuclease, isolated from the nuclei of normal human and xeroderma pigmentosum complementation group A (XPA) cells, which recognizes predominately pyrimidine dimers, was examined for the mechanism by which it locates sites of damage on UVC-irradiated DNA. In reaction mixtures with low ionic strengths (i.e. lacking KCl), the normal and XPA endonuclease locate sites of UV damage on both naked and reconstituted nucleosomal DNA by different mechanisms. On both of these substrates, the normal endonuclease acts by a processive mechanism, meaning that it binds non-specifically to DNA and scans the DNA for sites of damage, whereas the XPA endonuclease acts by a distributive one, meaning that it randomly locates sites of damage on DNA. However, while both the normal and XPA endonucleases can incise UVC irradiated naked DNA, they differ in ability to incise damaged nucleosomal DNA. The normal endonuclease showed increased activity on UVC treated nucleosomal DNA compared with naked DNA, whereas the XPA endonuclease showed decreased activity on the damaged nucleosomal substrate. Since a processive mechanism of action is sensitive to the ionic strength of the micro-environment, the KCl concentration of the reaction was increased. At 70 mM KCI, the normal endonuclease switched to a distributive mechanism of action and its ability to incise damaged nucleosomal DNA also decreased. These studies show that there is a correlation between the ability of these endonucleases to act by a processive mechanism and their ability to incise damaged nucleosomal DNA; the normal endonuclease, which acts processively, can incise damaged nucleosomal DNA, whereas the XPA endonuclease, which acts distributively, is defective in ability to incise this substrate.      

A new amino acid mixture permits new approaches to the treatment of phenylketonuria

A new amino acid mixture for incorporation into medical foods for the treatment of hyperphenylalaninemia has been tested in a regular clinic. The mix is designed to be as unobtrusive as possible, consistent with good nutrition. After more than 1 year of trial as a beverage, we have shown that it is safe and well tolerated but that plasma phenylalanine is no better controlled than with some other products. The mix can be incorporated into a large number of different foods without affecting the taste. Occult monitoring of the quantity of medical foods purchased compared with the amounts reported to be consumed in diet histories provides an excellent way to monitor dietary compliance.     

T-cells in alzheimer’s disease

Alzheimer’s disease (AD) is the most common dementing illness and is pathologically characterized by deposition of the 40–42 amino acid peptide, amyloid-β (Aβ), as senile plaques. It is well documented that brain inflammatory mechanisms mediated by reactive glia are activated in response to Aβ plaques. A number of reports further suggest that T-cells are activated in AD patients, and that these cells exist both in the periphery and as infiltrates in the brain. We explore the potential role of T-cells in the AD process, a controversial area, by reviewing reports that show disturbed activation profiles and/or altered numbers of various subsets of T-cells in the circulation as well as in the AD brain parenchyma and in cerebral amyloid angiopathy. We also discuss the recent Aβ immunotherapy approach vis-à-vis the activated, autoaggressive T-cell infiltrates that contributed to aseptic meningoencephalitis in a small percentage of patients, and present possible alternative approaches that may be both efficacious and safe. Finally, we explore the use of mouse models of AD as a system within which to definitively test the possible contribution of T-cells to AD pathogenesis.     

CD45 isoform RB as a molecular target to oppose lipopolysaccharide-induced microglial activation in mice

CD45 is a membrane-bound protein tyrosine phosphatase expressed on all hemopoietic cells with multiple splice variants, including RA, RB, RC and RO. Our previous studies have shown that cross-linking of CD45 with an anti-CD45 antibody markedly inhibits LPS-induced microglia activation. In order to determine which of the CD45 isoforms may be responsible for these effects, we have investigated the expression of CD45 isoforms on cultured microglial cells using flow cytometric analysis. Data reveal that CD45RB is the predominant isoform expressed in murine primary cultured microglial cells. Furthermore, incubation of these cultured cells with anti-CD45RB antibody results in a reduction of microglial activation induced by LPS as evidenced by TNF-alpha production. As a validation of these findings in vivo, brain homogenates from anti-CD45RB antibody (MG23G2)-injected animals that had been treated with LPS demonstrate a significant decrease in TNF-alpha levels compared to control mice treated with LPS plus vehicle. Taken together, these findings suggest that therapeutic agents that specifically stimulate the microglial CD45RB signaling pathway may be effective in suppressing microglial activation associated with several neurodegenerative disorders.     

Psychopathology and illness beliefs influence COPD self-management

OBJECTIVE: To explore the influence of psychological characteristics in Chronic Obstructive Pulmonary Disease (COPD) self-management. METHODS: Patients admitted with an exacerbation of COPD were interviewed for psychiatric symptoms, illness beliefs and self-management behaviour using a new COPD Self-Management Interview (COPD-SMI). This comprised three scenarios to mimic a future evolving exacerbation. Responses were scored for knowledge and actions (adherence) for each scenario. RESULTS: Of 47 people approached, 39 participated; 41% had panic attacks, 33% general anxiety, 35% a depression history, 31% an anxiety history and 21% an alcohol dependence history. Twenty-six (67%) had a self-management plan. When hypothetically "well" lower (poorer) COPD-SMI Knowledge Scores were associated with an alcohol dependence history (P=.025), no panic (P=.021) and males (P=.028). Those perceiving less influence over COPD had lower Action Scores during this scenario (P=.01) and the "early exacerbation" scenario (P=.05). Lower Knowledge Scores for the "early exacerbation" were associated with no panic (P=.01) and no self-management plans (P=.03). For the "severe exacerbation", lower Action Scores were associated with depression history (P=.004), panic (P=.002), higher FEV(1)% and no self-management plans (P=.005). Higher PaCO(2) was associated with lower confidence in symptom recognition, self-management ability and medical care influencing COPD. CONCLUSION: Anxiety, depression, alcohol use and illness beliefs may differentially influence self-management. Depression, previous alcohol dependence and perceived less influence over COPD inhibited self-management. Those with panic demonstrated more self-management knowledge when "well" but performed poorly on actions during the "severe exacerbation". Those with self-management plans had better knowledge and actions.