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The guanylyl cyclase-activating protein 1, GCAP1, activates or inhibits retinal guanylyl cyclase (retGC) depending on cellular Ca2+ concentrations. Several point mutations of GCAP1 have been associated with impaired calcium sensitivity that eventually triggers progressive retinal degeneration. In this work, we demonstrate that the recombinant human protein presents a highly dynamic monomer-dimer equilibrium, whose dissociation constant is influenced by salt concentration and, more importantly, by protein binding to Ca2+ or Mg2+. Based on small-angle X-ray scattering data, protein-protein docking, and molecular dynamics simulations we propose two novel three-dimensional models of Ca2+-bound GCAP1 dimer. The different propensity of human GCAP1 to dimerize suggests structural differences induced by cation binding potentially involved in the regulation of retGC activity.

Human T-lymphotropic viruses type 1 (HTLV-1) and type 2 (HTLV-2) present very similar genomic structures but HTLV-1 is more pathogenic than HTLV-2. Is this difference due to their transactivating Tax proteins, Tax-1 and Tax-2, which are responsible for viral and cellular gene activation? Do Tax-1 and Tax-2 differ in their cellular localization and in their interaction pattern with cellular factors? In this review, we summarize Tax-1 and Tax-2 structural and phenotypic properties, their interaction with factors involved in signal transduction and their localization-related behavior within the cell. Special attention will be given to the distinctions between Tax-1 and Tax-2 that likely play an important role in their transactivation activity.

HTLV-1 is more pathogenic than HTLV-2 despite having a similar genome and closely related transactivating oncoproteins. Both Tax-1 protein from HTLV-1 and Tax-2 from HTLV-2 activate the NF-κB pathway. The mechanisms involved in Tax-1 deregulation of this signalling pathway have been thoroughly investigated, but little is known about regulation by Tax-2. We have compared the interaction of Tax-1 and Tax-2 with two key NF-κB signalling factors: TAK1-binding protein 2 (TAB2), an adaptor involved in the activation of TAK1 kinase, and RelA, the active subunit of the canonical RelA/p50 NF-κB transcription factor. Tax-2 formed stable complexes with both RelA and TAB2. These two NF-κB factors colocalized with Tax proteins in dotted cytoplasmic structures targeted by calreticulin, a multi-process calcium-buffering chaperone. Co-expression of RelA and/or TAB2 markedly increased Tax-mediated NF-κB activation. These findings provide new insights into the role of RelA, TAB2 and Tax in the deregulation of the NF-κB pathway.

Synapse competition and elimination are a general developmental process both in central and in peripheral nervous systems that is strongly activity dependent. Some common features regulate synapse competition, and one of these is an application to development of the Hebb's postulate of learning: repeated coincident spike activity in competing presynaptic inputs on the same target cell inhibits competition, whereas noncoincident activity promotes weakening of some of the inputs and ultimately their elimination. Here we report experiments that indicate that the development of muscle innervation (initial polyneuronal innervation and subsequent synapse elimination) follows the Hebb's paradigm. We utilized two different models of muscle reinnervation in the adult rat: 1) we crushed nerves going to soleus or extensor digitorum longus muscles, to activate regeneration of the presynaptic component of the neuromuscular junctions (NMJ), or 2) we injected the soleus muscle with Marcaine (a myotoxic agent) to activate regeneration of the postsynaptic component, the muscle fiber. A condition of transient polyneuronal innervation occurs during NMJ regeneration in both cases, although the two models differ insofar as the relative strength of the competing inputs is concerned. During the period of competition (a few days or weeks, in Marcaine or crush experiments, respectively), we imposed a synchronous firing pattern on the competing inputs by stimulating motor axons distal to a chronic conduction block and demonstrated that this procedure strongly inhibits synapse elimination, with respect to control muscles in which regeneration occurs under natural impulse activity of motoneurons.

Background Human T cell lymphotropic virus type 1 (HTLV-1) is the etiological agent of a severe form of neoplasia designated Adult T cell Leukaemia (ATL). It is widely accepted that the viral transactivator Tax-1 is the major viral product involved in the onset, but not in the maintenance, of neoplastic phenotype, as only 30–40% of ATL cells express Tax-1. It has been recently demonstrated that HBZ (HTLV-1 bZIP factor), a protein encoded by the minus strand of HTLV-1 genome, constantly expressed in infected cells and in ATL tumor cells, is also involved in the pathogenesis of leukaemia. The full role played by HBZ in oncogenesis is not clarified in detail also because of the limited availability of tools to assess quantitative expression, subcellular location and interaction of HBZ with host factors in ATL. Results By the use of the first reported monoclonal antibody against HBZ, 4D4-F3, generated in our laboratory it has been possible to carefully assess for the first time the above parameters in HTLV-1 chronically infected cells and, most importantly, in fresh leukemic cells from patients. Endogenous HBZ is expressed in speckle-like structures localized in the nucleus. The calculated number of endogenous HBZ molecules varies between 17.461 and 39.615 molecules per cell, 20- to 50-fold less than the amount expressed in HBZ transfected cells used by most investigators to assess the expression, function and subcellular localization of the viral protein. HBZ interacts in vivo with p300 and JunD and co-localizes only partially, and depending on the amount of expressed HBZ, not only with p300 and JunD but also with CBP and CREB2. Conclusions The possibility to study endogenous HBZ in detail may significantly contribute to a better delineation of the role of HBZ during HTLV-1 infection and cellular transformation. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0186-0) contains supplementary material, which is available to authorized users.

Synapse elimination is a widespread developmental process in the peripheral and central nervous system that brings about refinement of neural connections through epigenetic mechanisms. Here we describe recent advances concerning the role of the pattern of motoneuronal firing, synchronous or asynchronous, in neuromuscular synapse elimination.

Individual synaptic sites on rodent skeletal muscle fibers are innervated by two or more axons at birth. All inputs but one are then eliminated during the first two postnatal weeks, leaving each muscle fiber singly innervated ([ 1 ][1]). Quattrocchi et al . ([ 2 ][2]) reported that polyneuronal

Background A possible association between human cytomegalovirus (HCMV) infection and colorectal cancer progression has been inferred by the identification in tumour tissues of HCMV antigens and specific viral DNA or RNA sequences. To further investigate the relationship between HCMV and colorectal cancers we developed qualitative and quantitative PCR assay to detect HCMV DNA in 56 formalin-fixed paraffin-embedded (FFPE) tissue samples from patients belonging to 4 different histological phenotypes: adenoma; poorly, moderately and well differentiated adenocarcinomas. Results Of the 56 FFPE tested tissue samples, 6 (11%) were positive for HCMV nested PCR amplification, and more precisely 1 (5%) of 20 cases of adenoma and 5 (21%) of 24 cases of moderately differentiated adenocarcinoma. No PCR positivity was obtained in samples from well and poorly differentiated adenocarcinomas. Conclusion Our observations suggest that there is no evidence of a direct association between HCMV and colorectal cancer. Moreover, the results obtained are not supportive of a causal role of HCMV in the processes of carcinogenesis and/or progression of colorectal cancer. However, the fact that the virus may present a "hit and run" like-mechanism and HCMV can thus only be detectable at a particular stage of a processing adenocarcinoma, suggests that a significant number of colorectal cancers might have been the subject of HCMV infection that could contribute to trigger the oncogenic differentiation. Our analysis does not exclude the possibility of HCMV infection subsequent viral clearance.