Mutations affecting ciliary components cause a series of related genetic disorders in humans, including nephronophthisis (NPHP), Joubert syndrome (JBTS), Meckel-Gruber syndrome (MKS), and Bardet-Biedl syndrome (BBS), which are collectively termed "ciliopathies." Recent protein-protein interaction studies combined with genetic analyses revealed that ciliopathy-related proteins form several functional networks/modules that build and maintain the primary cilium. However, the precise function of many ciliopathyrelated proteins and the mechanisms by which these proteins are targeted to primary cilia are still not well understood. Here, we describe a protein-protein interaction network of inositol polyphosphate-5-phosphatase E (INPP5E), a prenylated protein associated with JBTS, and its ciliary targeting mechanisms. INPP5E is targeted to the primary cilium through a motif near the C terminus and prenyl-binding protein phosphodiesterase 6D (PDE6D)-dependent mechanisms. Ciliary targeting of INPP5E is facilitated by another JBTS protein, ADP-ribosylation factor-like 13B (ARL13B), but not by ARL2 or ARL3. ARL13B missense mutations that cause JBTS in humans disrupt the ARL13B-INPP5E interaction. We further demonstrate interactions of INPP5E with several ciliary and centrosomal proteins, including a recently identified ciliopathy protein centrosomal protein 164 (CEP164). These findings indicate that ARL13B, INPP5E, PDE6D, and CEP164 form a distinct functional network that is involved in JBTS and NPHP but independent of the ones previously defined by NPHP and MKS proteins.photoreceptor degeneration | retinitis pigmentosa | leber congenital amaurosis | polydactyly | cystic kidney P rimary cilia are microtubule-based cell surface projections that emanate from the centrosome. This subcellular organelle functions as an antenna, sensing and transducing extracellular signals into the cell, and plays an essential role in regulating multiple cellular processes including the cell cycle, embryonic development, and tissue homeostasis (1-3). Mutations affecting ciliary and centrosomal components underlie a group of related human disorders such as Joubert syndrome (JBTS), Meckel-Gruber syndrome (MKS), nephronophthisis (NPHP), and Bardet-Biedl syndrome (BBS), collectively termed ciliopathies (1-3). Recent proteinprotein interaction studies have identified several functional modules or networks involved in these ciliopathies (4). For example, BBS proteins and intraflagellar transport (IFT) proteins form multiprotein complexes, the BBSome and the IFT complexes, respectively, and these complexes are involved in transporting ciliary proteins. Likewise, NPHP and MKS proteins form a distinct modular complex at the transition zone of primary cilia and regulate ciliary membrane compositions (5-9). However, there are many ciliary and centrosomal proteins [e.g., inositol polyphosphate-5-phosphatase E (INPP5E) and ADP-ribosylation factor-like 13B (ARL13B)] that have not been linked to any of the known functional networks and their precise functions ...

The CD4+ and CD8+ T cell dichotomy is essential for effective cellular immunity. How the individual T cell identity is established remains poorly understood. Here we show that the high mobility group (HMG) transcription factors Tcf1 and Lef1 are essential for repressing CD4+ lineage-associated genes including Cd4, Foxp3 and Rorc in CD8+ T cells. Tcf1- and Lef1-deficient CD8+ T cells exhibit histone hyperacetylation, which is ascribed to an unexpected intrinsic histone deacetylase (HDAC) activity in Tcf1 and Lef1. Mutating five conserved amino acids in the Tcf1 HDAC domain diminishes the HDAC activity and the ability to suppress CD4+ lineage genes in CD8+ T cells. These findings reveal that sequence-specific transcription factors can utilize intrinsic HDAC activity to guard cell identity by repressing lineage-inappropriate genes.

The de novo synthesis of pyrimidine nucleotides is required for mammalian cells to proliferate. The rate-limiting step in this pathway is catalysed by carbamoyl phosphate synthetase (CPS II), part of the multifunctional enzyme CAD. Here we describe the regulation of CAD by the mitogen-activated protein (MAP) kinase cascade. When phosphorylated by MAP kinase in vitro or activated by epidermal growth factor in vivo, CAD lost its feedback inhibition (which is dependent on uridine triphosphate) and became more sensitive to activation (which depends upon phosphoribosyl pyrophosphate). Both these allosteric regulatory changes favour biosynthesis of pyrimidines for growth. They were accompanied by increased epidermal growth factor-dependent phosphorylation of CAD in vivo and were prevented by inhibition of MAP kinase. Mutation of a consensus MAP kinase phosphorylation site abolished the changes in CAD allosteric regulation that were stimulated by growth factors. Finally, consistent with an effect of MAP kinase signalling on CPS II activity, epidermal growth factor increased cellular uridine triphosphate and this increase was reversed by inhibition of MAP kinase. Hence these studies may indicate a direct link between activation of the MAP kinase cascade and de novo biosynthesis of pyrimidine nucleotides.

Chronic bacterial lung infections in cystic fibrosis (CF) are caused by defects in the CF transmembrane conductance regulator chloride channel. Previously, we described that newborn CF transmembrane conductance regulator-knockout ferrets rapidly develop lung infections within the first week of life. Here, we report a more slowly progressing lung bacterial colonization phenotype observed in juvenile to adult CF ferrets reared on a layered antibiotic regimen. Even on antibiotics, CF ferrets were still very susceptible to bacterial lung infection. The severity of lung histopathology ranged from mild to severe, and variably included mucus obstruction of the airways and submucosal glands, air trapping, atelectasis, bronchopneumonia, and interstitial pneumonia. In all CF lungs, significant numbers of bacteria were detected and impaired tracheal mucociliary clearance was observed. Although Streptococcus, Staphylococcus, and Enterococcus were observed most frequently in the lungs of CF animals, each animal displayed a predominant bacterial species that accounted for over 50% of the culturable bacteria, with no one bacterial taxon predominating in all animals. Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry fingerprinting was used to quantify lung bacteria in 10 CF animals and demonstrated Streptococcus, Staphylococcus, Enterococcus, or Escherichia as the most abundant genera. Interestingly, there was significant overlap in the types of bacteria observed in the lung and intestine of a given CF animal, including bacterial taxa unique to the lung and gut of each CF animal analyzed. These findings demonstrate that CF ferrets develop lung disease during the juvenile and adult stages that is similar to patients with CF, and suggest that enteric bacterial flora may seed the lung of CF ferrets.

Herpes simplex virus type 1 utilizes cell surface heparan sulfate as receptors to infect target cells. The unique heparan sulfate saccharide sequence offers the binding site for viral envelope proteins and plays critical roles in assisting viral infections. A specific 3-O-sulfated heparan sulfate is known to facilitate the entry of herpes simplex virus 1 into cells. The 3-O-sulfated heparan sulfate is generated by the heparan sulfate D-glucosaminyl-3-O-sulfotransferase isoform 3 (3-OST-3), and it provides binding sites for viral glycoprotein D (gD). Here, we report the purification and structural characterization of an oligosaccharide that binds to gD. The isolated gDbinding site is an octasaccharide, and has a binding affinity to gD around 18 M, as determined by affinity coelectrophoresis. The octasaccharide was prepared and purified from a heparan sulfate oligosaccharide library that was modified by purified 3-OST-3 enzyme. The molecular mass of the isolated octasaccharide was determined using both nanoelectrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. The results from the sequence analysis suggest that the structure of the octasaccharide is a heptasulfated octasaccharide. The proposed structure of the octasaccharide is ⌬UA-GlcNSIdoUA2S-GlcNAc-UA2S-GlcNS-IdoUA2S-GlcNH 2 3S6S. Given that the binding of 3-O-sulfated heparan sulfate to gD can mediate viral entry, our results provide structural information about heparan sulfate-assisted viral entry.Heparan sulfates (HS), 1 highly sulfated polysaccharides, are present on the surface of mammalian cells and in the extracellular matrix in large quantities. HS play critical roles in a variety of biological interactions, including assisting viral infection, regulating blood coagulation and embryonic development, suppressing tumor growth, and controlling the eating behavior of mice by interacting with specific regulatory proteins (1-5). HS is initially synthesized as a copolymer of glucuronic acid and N-acetylated glucosamine by D-glucuronyl and N-acetyl-D-glucosaminyl transferase, followed by various modifications (6). These modifications include C 5 -epimerization of glucuronic acid to form iduronic acid residues, 2-O-sulfation of iduronic and glucuronic acid, N-deacetylation and N-sulfation of glucosamine, as well as 6-O-sulfation and 3-O-sulfation of glucosamine. Numerous HS biosynthetic enzymes have been cloned and characterized (for review, see Esko and Lindahl (7)).The specific sulfated saccharide sequences play critical roles in determining the functions of HS. A recent report suggests that the expression levels of various isoforms of each class of HS biosynthetic enzyme contribute to the synthesis of specific saccharide sequences in specific tissues (8). HS N-deacetylase/ N-sulfotransferase, 3-O-sulfotransferase, and 6-O-sulfotransferase are present in multiple isoforms, and each isoform is believed to recognize the saccharide sequence around the modification site to generate a specific sulfated saccharid...