Preparation and purification of antibodies specific to human neuronal voltage-dependent calcium channel subunits

Dok proteins are recruited to the phagosome and degraded in a GP63-dependent manner during Leishmania major infection

Three adaptor molecules of the Dok family, Dok-1, Dok-2 and Dok-3 are expressed in macrophages and are involved in the negative regulation of signaling in response to lipopolysaccharide and various cytokines and growth factors. We investigated the role and the fate of these proteins following infection with Leishmania major promastigotes in macrophages. The protozoan parasite L. major causes cutaneous leishmaniasis and is known for its capacity to alter host-cell signaling and function. Dok-1/Dok-2(-/-) bone marrow-derived macrophages displayed normal uptake of L. major promastigotes. Following Leishmania infection, Dok-1 was barely detectable by confocal microscopy. By contrast, phagocytosis of latex beads or zymosan led to the recruitment of Dok-1 to phagosomes. In the absence of the Leishmania pathogenesis-associated metalloprotease GP63, Dok-1 was also, partially, recruited to phagosomes containing L. major promastigotes. Further biochemical analyses revealed that similar to Dok-1, Dok-2 and Dok-3 were targets of GP63. Moreover, we showed that upon infection with wild-type or Δgp63 L. major promastigotes, production of nitric oxide and tumor necrosis factor by interferon-γ-primed Dok-1/Dok-2(-/-) macrophages was reduced compared to WT macrophages. These results suggest that Dok proteins may be important regulators of macrophage responses to Leishmania infection.

Dok-1 overexpression promotes development of γδ natural killer T cells

In T cells, two members of the Dok family, Dok-1 and Dok-2, are predominantly expressed. Recent evidence suggests that they play a negative role in T-cell signaling. In order to define whether Dok proteins regulate T-cell development, we have generated transgenic mice overexpressing Dok-1 in thymocytes and peripheral T cells. We show that overexpression of Dok-1 retards the transition from the CD4(-) CD8(-) to CD4(+) CD8(+) stage. Moreover, there is a specific expansion of PLZF-expressing Vγ1.1(+) Vδ6.3(+) T cells. This subset of γδ T cells acquires innate characteristics including rapid IL-4 production following stimulation and requiring SLAM-associated adaptor protein (SAP) for their development. Moreover, Dok-1 overexpression promotes the generation of an innate-like CD8(+) T-cell population that expresses Eomesodermin. Altogether, these findings identify a novel role for Dok-1 in the regulation of thymic differentiation and in particular, in the development of PLZF(+) γδ T cells.

Transgenic expression of the activating natural killer receptor Ly49H confers resistance to cytomegalovirus in genetically susceptible mice

Natural resistance to infection with mouse cytomegalovirus (MCMV) is controlled by a dominant locus, Cmv1. Cmv1 is linked to the Ly49 family of natural killer receptors on distal chromosome 6. While some studies localized Cmv1 as distal to the Ly49 gene cluster, genetic and functional analysis identified Ly49h as a pivotal factor in resistance to MCMV. The role of these two independent genomic domains in MCMV resistance was evaluated by functional complementation using transgenesis of bacterial artificial chromosomes (BAC) in genetically susceptible mice. Phenotypic and genetic characterization of the transgenic animals traced the resistance gene to a single region spanning the Ly49h gene. The appearance of the Ly49H protein in NK cells of transgenic mice coincided with the emergence of MCMV resistance, and there was a threshold Ly49H protein level associated with full recovery. Finally, transgenic expression of Ly49H in the context of either of the two independent susceptibility alleles, Cmv1(sBALB) or Cmv1(sFVB), conferred resistance to MCMV infection. These results demonstrate that Ly49h is necessary and sufficient to confer MCMV resistance, and formally demonstrate allelism between Cmv1 and Ly49h. This panel of transgenic animals provides a unique resource to study possible pleiotropic effect of Cmv1.

The status of voltage-dependent calcium channels in alpha 1E knock-out mice

It has been hypothesized that R-type Ca currents result from the expression of the alpha(1E) gene. To test this hypothesis we examined the properties of voltage-dependent Ca channels in mice in which the alpha(1E) Ca channel subunit had been deleted. Application of omega-conotoxin GVIA, omega-agatoxin IVA, and nimodipine to cultured cerebellar granule neurons from wild-type mice inhibited components of the whole-cell Ba current, leaving a "residual" R current with an amplitude of approximately 30% of the total Ba current. A minor portion of this R current was inhibited by the alpha(1E)-selective toxin SNX-482, indicating that it resulted from the expression of alpha(1E). However, the majority of the R current was not inhibited by SNX-482. The SNX-482-sensitive portion of the granule cell R current was absent from alpha(1E) knock-out mice. We also identified a subpopulation of dorsal root ganglion (DRG) neurons from wild-type mice that expressed an SNX-482-sensitive component of the R current. However as with granule cells, most of the DRG R current was not blocked by SNX-482. We conclude that there exists a component of the R current that results from the expression of the alpha(1E) Ca channel subunit but that the majority of R currents must result from the expression of other Ca channel alpha subunits.

Distribution of the voltage-dependent calcium channel alpha1G subunit mRNA and protein throughout the mature rat brain

The molecular identity of a gene which encodes the pore-forming subunit (alpha1G) of a member of the family of low-voltage-activated, T-type, voltage-dependent calcium channels has been described recently. Although northern mRNA analyses have shown alpha1G to be expressed predominantly in the brain, the detailed cellular distribution of this protein in the central nervous system (CNS) has not yet been reported. The current study describes the preparation of a subunit specific alpha1G riboprobe and antiserum which have been used in parallel in situ mRNA hybridization and immunohistochemical studies to localize alpha1G in the mature rat brain. Both alpha1G mRNA and protein were widely distributed throughout the brain, but variations were observed in the relative level of expression in discrete nuclei. Immunoreactivity for alpha1G was typically localized in both the soma and dendrites of many neurons. Whilst alpha1G protein and mRNA expression were often observed in cells known to exhibit T-type current activity, some was also noted in regions, e.g. cerebellar granule cells, in which T-type activity has not been described. These observations may reflect differences between the subcellular distribution of channels that can be identified by immunohistochemical methods compared with electrophysiological techniques.

The expression of voltage-dependent calcium channel beta subunits in human hippocampus

The beta subunits of voltage-dependent calcium channels (VDCC) modulate the electrophysiology and cell surface expression of pore-forming alpha1 subunits. In the present study we have investigated the distribution of beta1,beta2,beta3 and beta4 in the human hippocampus using in situ hybridization (ISH) and immunohistochemistry. ISH studies showed a similar distribution of expression of beta1,beta2 and beta3 subunit mRNAs, including labelling of the dentate granule cell layer, all CA pyramidal regions, and the subiculum. Relatively low levels of expression of beta1 and beta2 subunit mRNAs correlated with low protein expression in the immunocytochemical (ICC) studies. There was a relative lack of beta4 expression by both ISH and ICC in the CA1 region, compared with high levels of expression in the subiculum. Immunostaining for beta1 and beta2 subunits was weak and relatively homogeneous throughout the hippocampus. The beta3 and beta4 subunits appeared to be more discretely localized. In general, beta3-immunoreactivity was moderate both in cell bodies, and as diffuse staining in the surrounding neuropil. Strongest staining was observed in mossy fibres and their terminal region in the CA3 stratum lucidum. In contrast, beta4-immunoreactivity in the neuropil showed intense dendritic localisation. Unlike the other subunits, beta4-immunoreactivity was absent from CA1 pyramidal neurones but was present in a small population of interneurone-like cells. The localisation of beta3 and beta4 may represent presynaptic and postsynaptic compartments in some populations of hippocampal neurones. Comparison of beta subunit distribution with previously published data on alpha1 subunits indicates certain neuronal groups and subcellular compartments in which the subunit composition of native pre- and postsynaptic VDCC can be predicted.