The centrosome functions as the main microtubule-organizing center of animal cells and is crucial for several fundamental cellular processes. Abnormalities in centrosome number and composition correlate with tumor progression and other diseases. Although proteomic studies have identified many centrosomal proteins, their interactions are incompletely characterized. The lack of information on the precise localization and interaction partners for many centrosomal proteins precludes comprehensive understanding of centrosome biology. Here, we utilize a combination of selective chemical crosslinking and superresolution microscopy to reveal novel functional interactions among a set of 31 centrosomal proteins. We reveal that Cep57, Cep63, and Cep152 are parts of a ring-like complex localizing around the proximal end of centrioles. Furthermore, we identify that STIL, together with HsSAS-6, resides at the proximal end of the procentriole, where the cartwheel is located. Our studies also reveal that the known interactors Cep152 and Plk4 reside in two separable structures, suggesting that the kinase Plk4 contacts its substrate Cep152 only transiently, at the centrosome or within the cytoplasm. Our findings provide novel insights into protein interactions critical for centrosome biology and establish a toolbox for future studies of centrosomal proteins.

In addition to being instrumental to the protection of mucosal epithelia, secretory IgA (SIgA) adheres to and is transported by intestinal Peyer’s patch (PP) M cells. The possible functional reason for this transport is unknown. We have thus examined in mice the outcome of SIgA delivered from the intestinal lumen to the cells present in the underlying organized mucosa-associated lymphoreticular tissue. We show selective association of SIgA with dendritic cells and CD4+ T and B lymphocytes recovered from PP in vitro. In vivo, exogenously delivered SIgA is able to enter into multiple PP lining the intestine. In PP, SIgA associates with and is internalized by dendritic cells in the subepithelial dome region, whereas the interaction with CD4+ T cells is limited to surface binding. Interaction between cells and SIgA is mediated by the IgA moiety and occurs for polymeric and monomeric molecular forms. Thus, although immune exclusion represents the main function of SIgA, transport of the Ab by M cells might promote Ag sampling under neutralizing conditions essential to the homeostasis of mucosal surfaces.

Background: Interleukin-7 is the master regulator of T-cell proliferation. Results: IL-7 drives its receptor in a membrane microdomain that regulates phosphorylation of associated tyrosine kinases JAK1 and JAK3, anchors IL-7 receptor to cytoskeleton and regulates STAT5 phosphorylation and nuclear translocation. Conclusion: Membrane microdomains and cytoskeleton scaffold IL-7R-signalosomes and assist signaling protein transport. Significance: Transient membrane and cytoskeleton organization shapes IL-7-signaling mechanisms in CD4 T-cells.

No abstract

In the central nervous system, the aggregation of receptors is crucial for synapse formation and function. To study the role of presynaptic terminals in the maintenance of postsynaptic specializations, we analyzed the synaptic contacts between Purkinje cells and neurons of the deep cerebellar nuclei in two in vivo models: the Lurcher and Purkinje cell-deficient (PCD) mutant mice. These mutants lose their Purkinje cells at different postnatal stages. By using confocal scanner microscopy and immunohistochemistry, we studied the distribution of the alpha subunit of the gamma-aminobutyric acid (GABA)(A) receptor (GABA(A)Ralpha1) and gephyrin, one of its anchoring proteins, in relation to the distribution of presynaptic markers, glutamic acid decarboxylase (GAD), or synaptophysin. In Lurcher the distribution of GABA(A) receptor aggregates on the membrane of postsynaptic neurons was not affected by the important loss of GAD-positive terminals, whereas in PCD, the number of large GABA(A) receptor aggregates increased. In both mutants the number of aggregates of gephyrin decreased. Most of these remaining aggregates were clustered to form groups, some of which were in front of GAD-positive terminals. This study shows, for the first time, the localization of GABA(A)R alpha 1 in Lurcher and PCD mutant mice. It clearly establishes that GABA(A)R alpha 1 and gephyrin are differentially affected by deafferentation. Because the receptor aggregates are maintained while the gephyrin aggregates are lost, as a result some receptor aggregates are not associated with any gephyrin. These two postsynaptic components appeared to be regulated by different mechanisms.