Streptozocin Diabetes Elevates all Isoforms of TGF-β in the Rat Kidney

Transforming growth factor beta (TGF-β) is a major promoter of diabetic nephropathy. While TGF-β1 is the most abundaft renal isoform, types 2 and 3 are present as well and have identical in vitro effects. Whole kidney extracts were studied 2 weeks after induction of streptozocin diabetes and in control rats. Mean glomerular area was 25% greater in the diabetic animals. TGF-β1 showed a 2-fold increase in message with a 3-fold increase in protein. TGF-β2 mRNA increased approximately 6% while its protein doubled. TGF-β-message increased by 25%, producing a 35% increase in its protein. TGF-β- inducible gene H3 mRNA was increased 35% in the diabetic animals, consistent with increased activity of this growth factor. All isoforms of TGF-β are increased in the diabetic rat kidney. Future studies need to address the specific role that each isoform plays in diabetic nephropathy as well as the impact of therapies on each isoform

An Inner Centromere Protein that Stimulates the Microtubule Depolymerizing Activity of a KinI Kinesin

AbstractMitosis requires precise control of microtubule dynamics. The KinI kinesin MCAK, a microtubule depolymerase, is critical for this regulation. In a screen to discover previously uncharacterized microtubule-associated proteins, we identified ICIS, a protein that stimulates MCAK activity in vitro. Consistent with this biochemical property, blocking ICIS function in Xenopus extracts with antibodies caused excessive microtubule growth and inhibited spindle formation. Prior to anaphase, ICIS localized in an MCAK-dependent manner to inner centromeres, the chromosomal region located in between sister kinetochores. From Xenopus extracts, ICIS coimmunoprecipitated MCAK and the inner centromere proteins INCENP and Aurora B, which are thought to promote chromosome biorientation. By immunoelectron microscopy, we found that ICIS is present on the surface of inner centromeres, placing it in an ideal location to depolymerize microtubules associated laterally with inner centromeres. At inner centromeres, MCAK-ICIS may destabilize these microtubules and provide a mechanism that prevents kinetochore-microtubule attachment errors

Generation of both cortical and Aire(+) medullary thymic epithelial compartments from CD205(+) progenitors

In the adult thymus, the development of self-tolerant thymocytes requires interactions with thymic epithelial cells (TECs). Although both cortical and medullary TECs (cTECs/mTECs) are known to arise from common bipotent TEC progenitors, the phenotype of these progenitors and the timing of the emergence of these distinct lineages remain unclear. Here, we have investigated the phenotype and developmental properties of bipotent TEC progenitors during cTEC/mTEC lineage development. We show that TEC progenitors can undergo a stepwise acquisition of first cTEC and then mTEC hallmarks, resulting in the emergence of a progenitor population simultaneously expressing the cTEC marker CD205 and the mTEC regulator Receptor Activator of NF-κB (RANK). In vivo analysis reveals the capacity of CD205(+) TECs to generate functionally competent cortical and medullary microenvironments containing both cTECs and Aire(+) mTECs. Thus, TEC development involves a stage in which bipotent progenitors can co-express hallmarks of the cTEC and mTEC lineages through sequential acquisition, arguing against a simple binary model in which both lineages diverge simultaneously from bipotent lineage negative TEC progenitors. Rather, our data reveal an unexpected overlap in the phenotypic properties of these bipotent TECs with their lineage-restricted counterparts

Differential roles of CCL2 and CCR2 in host defense to coronavirus infection.

The CC chemokine ligand 2 (CCL2, monocyte chemoattractant protein-1) is important in coordinating the immune response following microbial infection by regulating T cell polarization as well as leukocyte migration and accumulation within infected tissues. The present study examines the consequences of mouse hepatitis virus (MHV) infection in mice lacking CCL2 (CCL2(-/-)) in order to determine if signaling by this chemokine is relevant in host defense. Intracerebral infection of CCL2(-/-) mice with MHV did not result in increased morbidity or mortality as compared to either wild type or CCR2(-/-) mice and CCL2(-/-) mice cleared replicating virus from the brain. In contrast, CCR2(-/-) mice displayed an impaired ability to clear virus from the brain that was accompanied by a reduction in the numbers of antigen-specific T cells as compared to both CCL2(-/-) and wild-type mice. The paucity in T cell accumulation within the central nervous system (CNS) of MHV-infected CCR2(-/-) mice was not the result of either a deficiency in antigen-presenting cell (APC) accumulation within draining cervical lymph nodes (CLN) or the generation of virus-specific T cells within this compartment. A similar reduction in macrophage infiltration into the CNS was observed in both CCL2(-/-) and CCR2(-/-) mice when compared to wild-type mice, indicating that both CCL2 and CC chemokine receptor 2 (CCR2) contribute to macrophage migration and accumulation within the CNS following MHV infection. Together, these data demonstrate that CCR2, but not CCL2, is important in host defense following viral infection of the CNS, and CCR2 ligand(s), other than CCL2, participates in generating a protective response

A Phospho-SIM in the Antiviral Protein PML is Required for Its Recruitment to HSV-1 Genomes

Herpes simplex virus type 1 (HSV-1) is a significant human pathogen that infects a large portion of the human population. Cells deploy a variety of defenses to limit the extent to which the virus can replicate. One such factor is the promyelocytic leukemia (PML) protein, the nucleating and organizing factor of nuclear domain 10 (ND10). PML responds to a number of stimuli and is implicated in intrinsic and innate cellular antiviral defenses against HSV-1. While the role of PML in a number of cellular pathways is controlled by post-translational modifications, the effects of phosphorylation on its antiviral activity toward HSV-1 have been largely unexplored. Consequently, we mapped phosphorylation sites on PML, mutated these and other known phosphorylation sites on PML isoform I (PML-I), and examined their effects on a number of PML’s activities. Our results show that phosphorylation at most sites on PML-I is dispensable for the formation of ND10s and colocalization between PML-I and the HSV-1 regulatory protein, ICP0, which antagonizes PML-I function. However, inhibiting phosphorylation at sites near the SUMO-interaction motif (SIM) of PML-I impairs its ability to respond to HSV-1 infection. Overall, our data suggest that PML phosphorylation regulates its antiviral activity against HSV-1

Identification of Mammalian Mediator Subunits with Similarities to Yeast Mediator Subunits Srb5, Srb6, Med11, and Rox3

The Mediator is a multiprotein coactivator required for activation of RNA polymerase II transcription by DNA binding transactivators. We recently identified a mammalian homologue of yeast Mediator subunit Med8 and partially purified a Med8-containing Mediator complex from rat liver nuclei (Brower, C. S., Sato, S., Tomomori-Sato, C., Kamura, T., Pause, A., Stearman, R., Klausner, R. D., Malik, S., Lane, W. S., Sorokina, I., Roeder, R. G., Conaway, J. W., and Conaway, R. C. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 10353-10358). Analysis of proteins present in the most highly purified Med8-containing fractions by tandem mass spectrometry led to the identification of many known mammalian Mediator subunits, as well as four potential Mediator subunits exhibiting sequence similarity to yeast Mediator subunits Srb5, Srb6, Med11, and Rox3. Here we present direct biochemical evidence that these four proteins are bona fide mammalian Mediator subunits. In addition, we identify direct pairwise binding partners of these proteins among the known mammalian Mediator subunits. Taken together, our findings identify a collection of novel mammalian Mediator subunits and shed new light on the underlying architecture of the mammalian Mediator complex