SLE-key(®) rule-out serologic test for excluding the diagnosis of systemic lupus erythematosus: Developing the ImmunArray iCHIP(®).

We describe here the development, verification and validation of the SLE-key(®) rule-out test for a definitive rule-out of a diagnosis of systemic lupus erythematosus (SLE). The test uses the proprietary iCHIP(®) micro-array technology platform (Fattal et al., 2010) to identify discriminating patterns of circulating autoantibodies among SLE patients compared with self-declared healthy individuals. Given the challenges associated with the diagnosis of SLE and the healthcare costs of delayed diagnosis and misdiagnosis, a definitive rule-out test can provide significant clinical benefits to patients and potentially major cost savings to healthcare systems.

Intracellular Na+ inhibits voltage-dependent N-type Ca2+ channels by a G protein betagamma subunit-dependent mechanism.

N-type voltage-dependent Ca(2+) channels (N-VDCCs) play important roles in neurotransmitter release and certain postsynaptic phenomena. These channels are modulated by a number of intracellular factors, notably by Gbetagamma subunits of G proteins, which inhibit N-VDCCs in a voltage-dependent (VD) manner. Here we show that an increase in intracellular Na(+) concentration inhibits N-VDCCs in hippocampal pyramidal neurones and in Xenopus oocytes. In acutely dissociated hippocampal neurones, Ba(2+) current via N-VDCCs was inhibited by Na(+) influx caused by the activation of NMDA receptor channels. In Xenopus oocytes expressing N-VDCCs, Ba(2+) currents were inhibited by Na(+) influx and enhanced by depletion of Na(+), after incubation in a Na(+)-free extracellular solution. The Na(+)-induced inhibition was accompanied by the development of VD facilitation, a hallmark of a Gbetagamma-dependent process. Na(+)-induced regulation of N-VDCCs is Gbetagamma dependent, as suggested by the blocking of Na(+) effects by Gbetagamma scavengers and by excess Gbetagamma, and may be mediated by the Na(+)-induced dissociation of Galphabetagamma heterotrimers. N-VDCCs may be novel effectors of Na(+)ion, regulated by the Na(+) concentration via Gbetagamma.

A novel long N-terminal isoform of human L-type Ca2+ channel is up-regulated by protein kinase C.

Human L-type voltage-dependent Ca(2+) channels (alpha(1C), or Ca(v)1.2) are up-regulated by protein kinase C (PKC) in native tissues, but in heterologous systems this modulation is absent. In rat and rabbit, alpha(1C) has two N-terminal (NT) isoforms, long and short, with variable initial segments of 46 and 16 amino acids, respectively. The initial 46 amino acids of the long-NT alpha(1C) are crucial for PKC regulation. However, only a short-NT human alpha(1C) is known. We assumed that a long-NT isoform of human alpha(1C) may exist. By homology screening of human genomic DNA, we identified a stretch (termed exon 1a) highly homologous to rabbit long-NT, separated from the next known exon of alpha(1C) (exon 1b, which encodes the alternative, short-NT) by an approximately 80 kb-long intron. The predicted 46-amino acid protein sequence is highly homologous to rabbit long-NT. Reverse transcriptase PCR showed the presence of exon 1a transcript in human cardiac RNA. Expression of human long-NT alpha(1C) in Xenopus oocytes produced Ca(2+) channel enhanced by a PKC activator, whereas the short-NT alpha(1C) was inhibited. The long-NT isoform may be the Ca(2+) channel enhanced by PKC-activating transmitters in human tissues.