A preliminary genetic association study of GAD1 and GABAB receptor genes in patients with treatment-resistant schizophrenia

Molecular Biology Reports - GABAergic system dysfunction has been implicated in the etiology of schizophrenia and of cognitive impairments in particular. Patients with treatment-resistant...     

Regulation of Hyaluronan (HA) Metabolism Mediated by HYBID (Hyaluronan-binding Protein Involved in HA Depolymerization,KIAA1199) and HA Synthases in Growth Factor-stimulated Fibroblasts

Regulation of hyaluronan (HA) synthesis and degradation is essential to maintenance of extracellular matrix homeostasis. We recently reported that HYBID (HYaluronan-Binding protein Involved in hyaluronan Depolymerization), also called KIAA1199, plays a key role in HA depolymerization in skin and arthritic synovial fibroblasts. However, regulation of HA metabolism mediated by HYBID and HA synthases (HASs) under stimulation with growth factors remains obscure. Here we report that TGF-β1, basic FGF, EGF, and PDGF-BB commonly enhance total amount of HA in skin fibroblasts through up-regulation of HAS expression, but molecular size of newly produced HA is dependent on HYBID expression levels. Stimulation of HAS1/2 expression and suppression of HYBID expression by TGF-β1 were abrogated by blockade of the MAPK and/or Smad signaling and the PI3K-Akt signaling, respectively. In normal human skin, expression of the TGF-β1 receptors correlated positively with HAS2 expression and inversely with HYBID expression. On the other hand, TGF-β1 up-regulated HAS1/2 expression but exerted only a slight suppressive effect on HYBID expression in synovial fibroblasts from the patients with osteoarthritis or rheumatoid arthritis, resulting in the production of lower molecular weight HA compared with normal skin and synovial fibroblasts. These data demonstrate that although TGF-β1, basic FGF, EGF, and PDGF-BB enhance HA production in skin fibroblasts, TGF-β1 most efficiently contributes to production of high molecular weight HA by HAS up-regulation and HYBID down-regulation and suggests that inefficient down-regulation of HYBID by TGF-β1 in arthritic synovial fibroblasts may be linked to accumulation of depolymerized HA in synovial fluids in arthritis patients.     

A Disintegrin and Metalloprotease 10 (ADAM10) Is Indispensable for Maintenance of the Muscle Satellite Cell Pool

Satellite cells (SCs) are muscle-specific stem cells that are essential for the regeneration of damaged muscles. Although SCs have a robust capacity to regenerate myofibers, the number of SCs decreases with aging, leading to insufficient recovery after muscle injury. We herein show that ADAM10 (a disintegrin and metalloprotease 10), a membrane-bound proteolytic enzyme with a critical role in Notch processing (S2 cleavage), is essential for the maintenance of SC quiescence. We generated mutant mice in which ADAM10 in SCs can be conditionally abrogated by tamoxifen injection. Tamoxifen-treated mutant mice did not show any apparent defects and grew normally under unchallenged conditions. However, these mice showed a nearly complete loss of muscle regeneration after chemically induced muscle injury. In situ hybridization and flow cytometric analyses revealed that the mutant mice had significantly less SCs compared with wild type controls. Of note, we found that inactivation of ADAM10 in SCs severely compromised Notch signaling and led to dysregulated myogenic differentiation, ultimately resulting in deprivation of the SC pool in vivo. Taken together, the present findings underscore the role of ADAM10 as an indispensable component of Notch signaling in SCs and for maintaining the SC pool.     

Dual DNA recognition codes of a short peptide derived from the basic leucine zipper protein EmBP1

Sequence-specific DNA binding of short peptide dimers derived from a plant basic leucine zipper protein EmBP1 was studied. A homodimer of the EmBP1 basic region peptide recognized a palindromic DNA sequence, and a heterodimer of EmBP1 and GCN4 basic region peptides targets a non-palindromic DNA sequence when a beta-cyclodextrin/adamantane complex is utilized as a dimerization domain. A homodimer of the EmBP1 basic region peptide binds the native EmBP1 binding 5'-GCCACGTGGC-3' and the native GCN4 binding 5'-ATGACGTCAT-3' sequences with almost equal affinity in the alpha-helical conformation, indicating that the basic region of EmBP1 by itself has a dual recognition codes for the DNA sequences. The GCN4 basic region peptide binds 5'-ATGAC-3' in the alpha-helical conformation, but it neither shows affinity nor helix formation with 5'-GCCAC-3'. Because native EmBP1 forms 100 times more stable complex with 5'-GCCACGTGGC-3' over 5'-ATGACGTCAT-3', our results suggest that the sequence-selectivity of native EmBP1 is dictated by the structure of leucine zipper dimerization domain including the hinge region spanning between the basic region and the leucine zipper.     

Roles of isoamylase and ADP-glucose pyrophosphorylase in starch granule synthesis in rice endosperm

Amyloplast-targeted green fluorescent protein (GFP) was used to monitor amyloplast division and starch granule synthesis in the developing endosperm of transgenic rice. Two classical starch mutants, sugary and shrunken, contain reduced activities of isoamylase1 (ISA1) and cytosolic ADP-glucose pyrophosphorylase, respectively. Dividing amyloplasts in the wild-type and shrunken endosperms contained starch granules, whereas those in sugary endosperm did not contain detectable granules, suggesting that ISA1 plays a role in granule synthesis at the initiation step. The transition from phytoglycogen to sugary-amylopectin was gradual in the boundary region between the inner and outer endosperms of sugary. These results suggest that the synthesis of sugary-amylopectin and phytoglycogen involved a stochastic process and that ISA1 activity plays a critical role in the stochastic process in starch synthesis in rice endosperm. The reduction of cytosolic ADP-glucose pyrophosphorylase activity in shrunken endosperm did not inhibit granule initiation but severely restrained the subsequent enlargement of granules. The shrunken endosperm often developed pleomorphic amyloplasts containing a large number of underdeveloped granules or a large cluster of small grains of amyloplasts, each containing a simple-type starch granule. Although constriction-type divisions of amyloplasts were much more frequent, budding-type divisions were also found in the shrunken endosperm. We show that monitoring GFP in developing amyloplasts was an effective means of evaluating the roles of enzymes involved in starch granule synthesis in the rice endosperm.