The Voltage-Gated Sodium Channel Na(v)1.8 Is Expressed in Human Sperm

The role of Na+ fluxes through voltage-gated sodium channels in the regulation of sperm cell function remains poorly understood. Previously, we reported that several genes encoding voltage-gated Na+ channels were expressed in human testis and mature spermatozoa. In this study, we analyzed the presence and function of the TTX-resistant VGSC a subunit Na(v)1.8 in human capacitated sperm cells. Using an RT-PCR assay, we found that the mRNA of the gene SCN10A, that encode Na-v1.8, was abundantly and specifically expressed in human testis and ejaculated spermatozoa. The Na-v1.8 protein was detected in capacitated sperm cells using three different specific antibodies against this channel. Positive immunoreactivity was mainly located in the neck and the principal piece of the flagellum. The presence of Na-v1.8 in sperm cells was confirmed by Western blot. Functional studies demonstrated that the increases in progressive motility produced by veratridine, a voltage-gated sodium channel activator, were reduced in sperm cells preincubated with TTX (10 mu M), the Na-v1.8 antagonist A-803467, or a specific Na-v1.8 antibody. Veratridine elicited similar percentage increases in progressive motility in sperm cells maintained in Ca2+-containing or Ca2+-free solution and did not induce hyperactivation or the acrosome reaction. Veratridine caused a rise in sperm intracellular Na+, [Na+](i), and the sustained phase of the response was inhibited in the presence of A-803467. These results verify that the Na+ channel Na-v1.8 is present in human sperm cells and demonstrate that this channel participates in the regulation of sperm function.

The promoter of cell growth- and RNA protection-associated SND1 gene is activated by endoplasmic reticulum stress in human hepatoma cells

Background: Staphyloccocal nuclease domain-containing protein 1 (SND1) is involved in the regulation of gene expression and RNA protection. While numerous studies have established that SND1 protein expression is modulated by cellular stresses associated with tumor growth, hypoxia, inflammation, heat- shock and oxidative conditions, little is known about the factors responsible for SND1 expression. Here, we have approached this question by analyzing the transcriptional response of human SND1 gene to pharmacological endoplasmic reticulum (ER) stress in liver cancer cells. Results: We provide first evidence that SND1 promoter activity is increased in human liver cancer cells upon exposure to thapsigargin or tunicamycin or by ectopic expression of ATF6, a crucial transcription factor in the unfolded protein response triggered by ER stress. Deletion analysis of the 5'-flanking region of SND1 promoter identified maximal activation in fragment (-934, +221), which contains most of the predicted ER stress response elements in proximal promoter. Quantitative real- time PCR revealed a near 3 fold increase in SND1 mRNA expression by either of the stress- inducers; whereas SND1 protein was maximally upregulated (3.4-fold) in cells exposed to tunicamycin, a protein glycosylation inhibitor. Conclusion: Promoter activity of the cell growth- and RNA-protection associated SND1 gene is up-regulated by ER stress in human hepatoma cells.

Brca1 is expressed in human microglia and is dysregulated in human and animal model of ALS

Background: There is growing evidence that microglia are key players in the pathological process of amyotrophic lateral sclerosis (ALS). It is suggested that microglia have a dual role in motoneurone degeneration through the release of both neuroprotective and neurotoxic factors. Results: To identify candidate genes that may be involved in ALS pathology we have analysed at early symptomatic age (P90), the molecular signature of microglia from the lumbar region of the spinal cord of hSOD1(G93A) mice, the most widely used animal model of ALS. We first identified unique hSOD1(G93A) microglia transcriptomic profile that, in addition to more classical processes such as chemotaxis and immune response, pointed toward the potential involvement of the tumour suppressor gene breast cancer susceptibility gene 1 (Brca1). Secondly, comparison with our previous data on hSOD1(G93A) motoneurone gene profile substantiated the putative contribution of Brca1 in ALS. Finally, we established that Brca1 protein is specifically expressed in human spinal microglia and is up-regulated in ALS patients. Conclusions: Overall, our data provide new insights into the pathogenic concept of a non-cell-autonomous disease and the involvement of microglia in ALS. Importantly, the identification of Brca1 as a novel microglial marker and as possible contributor in both human and animal model of ALS may represent a valid therapeutic target. Moreover, our data points toward novel research strategies such as investigating the role of oncogenic proteins in neurodegenerative diseases.