No abstract

The centrosomin (cnn) gene encodes a protein associated with mitotic centrosomes in Drosophila melanogaster and is a target of homeotic gene regulation. Here we report that CNN is an essential component of the centrosome. Loss of zygotic cnn expression disrupts the development of the second midgut constriction, the gastric caeca, and the nervous system. Embryos that lack maternal as well as zygotic cnn expression display defects in nuclear division, chromosome alignment, and microtubule organization, while adult flies that are mosaic for cnn-cells exhibit defects indicative of a block in cell proliferation. We propose that cnn provides an example of homeotic genes directly regulating the accumulation of essential cellular proteins to carry out segment-specific morphogenetic functions.

No abstract

Centrosomes and microtubules play crucial roles during cell division and differentiation. Spermatogenesis is a useful system for studying centrosomal function since it involves both mitosis and meiosis, and also transformation of the centriole into the sperm basal body. Centrosomin is a protein localized to the mitotic centrosomes in Drosophila melanogaster. We have found a novel isoform of centrosomin expressed during spermatogenesis. Additionally, an anticentrosomin antibody labels both the mitotic and meiotic centrosomes as well as the basal body. Mutational analysis shows that centrosomin is required for spindle organization during meiosis and for organization of the sperm axoneme. These results suggest that centrosomin is a necessary component of the meiotic centrosomes and the spermatid basal body.

No abstract

Ocular dryness and contact lens­(CL)-related microbial keratitis (MK) are two major risks of wearing CLs. The development of multifunctional surface coating for CLs with excellent hydrating and antimicrobial properties is a practical strategy to improve the comfort of CL wearers and to prevent corneal infection. Here, we develop zwitterionic and antimicrobial metal-phenolic networks (MPNs) based on the coordination of copper ions (CuII) and the poly­(carboxylbetaine-co-dopamine methacrylamide) copolymer (PCBDA), which can be easily one-step prepared onto CLs due to the near-universal adherent properties of catechol groups. The zwitterionic and antifouling carboxybetaine (CB) groups of the CuII–PCBDA coating can significantly increase the wettability of CLs and reduce their protein adsorptions, resulting in a lens surface that is more water retentive and with lower protein binding to prevent tear film evaporation and eye dryness. In addition, since the immobilized copper ions in the MPNs impart them with ion-mediated antimicrobial activity, the CuII–PCBDA coating exhibits a strong and broad-spectrum antimicrobial activity against MK related pathogenic microbes, including bacteria, such as Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, and fungi, such as Candida albicans. Compared with a pristine CL, the CuII–PCBDA-coated CL effectively inhibited biofilm formation even after daily exposure to the above microbial environment for 14 days. Notably, the CuII–PCBDA coating developed in this study is not only biocompatible with 100% cell viability following direct contact with human corneal epithelial cells (HCECs) for 48 h but also maintains the optical clarity of the native CLs. Thus, the CuII–PCBDA coating has a great application potential for the development of a multifunctional surface coating for CLs for increased CL comfort and prevention of MK.

No abstract

A novel regulator of G-protein signaling (RGS) has been isolated from a highly purified population of mouse long-term hematopoietic stem cells, and designated RGS18. It has 234 amino acids consisting of a central RGS box and short divergent NH 2 and COOH termini. The calculated molecular weight of RGS18 is 27,610 and the isoelectric point is 8.63. Mouse RGS18 is expressed from a single gene and shows tissue specific distribution. It is most highly expressed in bone marrow followed by fetal liver, spleen, and then lung. In bone marrow, RGS18 level is highest in long-term and shortterm hematopoietic stem cells, and is decreased as they differentiate into more committed multiple progenitors. The human RGS18 ortholog has a tissue-specific expression pattern similar to that of mouse RGS18. Purified RGS18 interacts with the ␣ subunit of both G i and G q subfamilies. The results of in vitro GTPase single-turnover assays using G␣ i indicated that RGS18 accelerates the intrinsic GTPase activity of G␣ i . Transient overexpression of RGS18 attenuated inositol phosphates production via angiotensin receptor and transcriptional activation through cAMP-responsive element via M1 muscarinic receptor. This suggests RGS18 can act on G q -mediated signaling pathways in vivo.A large number of extracellular stimuli act via cell surface receptors coupled to G-proteins (1). Inactive G-proteins are heterotrimeric proteins consisting of ␣, ␤, and ␥ subunits. Upon binding of a specific ligand to the G-protein-coupled receptor, the receptor promotes the exchange of GDP to GTP in the ␣ subunit, resulting in dissociation of the ␣ subunit from the ␤␥ subunits. The ␤␥ subunits are tightly associated and do not dissociate under physiological conditions. The free ␣ subunit and ␤␥ subunits then transmit signals through various signal transduction pathways. The activated ␣ subunit has slow intrinsic GTPase activity. When the ␣ subunit is in the GDPbound form, it re-associates with the ␤␥ subunits, leading to an inactive form. The duration of the G-protein signal depends on the rate of GTP hydrolysis and the rate of subunit re-association. For small GTP-binding proteins such as ras, there are GAP 1 proteins (GTPase activating protein), which increase the GTP hydrolysis rate. Recently, functional homologs of the ras-GAP have been identified for the heterotrimeric G-protein.These are called RGS (regulator of G-protein signaling) proteins. The first RGS identified, Sst2 (supersensitivity to pheromone) in yeast, is a negative regulator of pheromone signaling (2). Later, the SST2 gene product was shown to function as a GAP for Gpa1, a molecule involved in pheromone desensitization (3). So far ϳ20 RGS have been identified (4 -12), and more could be anticipated. All RGS proteins have a highly conserved domain consisting of 120 amino acid residues, the RGS box, with varying lengths of NH 2 and COOH termini. RGS4 can be expressed in bacteria, and it has been co-crystallized with G␣ i1 as the GDP-AlF4 Ϫ -bound form (13). It was shown that RGS binds to G␣ i t...