Social stress decreases marking behavior independently of testosterone in Mongolian gerbils

This study examined the endogenous androgen regulation of the marking behavior in Mongolian gerbils (Meriones unguiculatus). In the first experiment, developmental changes of fecal testosterone levels, ventral gland growth, and the marking frequency of male gerbils were investigated. From 9 weeks of age, marking frequency increased with increases in fecal testosterone levels and ventral gland size. The ventral gland size and marking frequency were significantly correlated to the fecal testosterone level. In the second experiment, we hypothesized that reduction in the marking frequency of subordinate males after social confrontations was controlled by a decrease in the circulating testosterone level, and we followed changes in marking frequency, endocrine status, and ventral gland size after social confrontations in which two adult male gerbils established their social ranks by fighting. As expected, marking frequency and ventral gland size were significantly related to social rank, that is, marking frequency was higher among dominant gerbils and lower among subordinates. In addition, fecal corticosterone levels among subordinates were higher than those of dominant animals. However, neither the fecal and plasma testosterone levels, nor testis size, differed between dominant and subordinate gerbils. These results revealed that endogenous androgen played a role in regulating marking behavior and ventral gland size during the developmental stage and that the reductions in marking frequency and ventral gland size occurring in subordinate males after social confrontations were not directly regulated by androgen changes.     

Identification of a key amino acid residue of Streptomyces phospholipase D for thermostability by in vivo DNA shuffling

To isolate thermostability-related amino acid residues of Streptomyces phospholipase D (PLD), we constructed a chimeral genes library between two highly homologous plds, which exhibited different thermostabilities, by an in vivo DNA shuffling method using Escherichia coli that has a mutation of a single-stranded DNA-binding protein gene. To confirm the location of the recombination site, we carried out the restriction mapping of 68 chimeral pld genes. The recombination sites were widely dispersed over the entire pld sequence. Moreover, we examined six chimeral PLDs by comparing their thermostabilities with those of parental PLDs. To identify a thermostability-related amino acid residue, we investigated the thermostability of chimera C that was the most thermolabile among the six chimeras. We identified the thermostability-related factor Gly-188, which is located in the alpha-7 helix of PLD from Streptomyces septatus TH-2 (TH-2PLD). TH-2PLD mutants, in which Gly-188 was substituted with Phe, Val or Trp, exhibited higher thermostabilities than that of the parental PLD. Gly-188 substituted with the Phe mutant, which was the most stable among the mutants, showed an enzyme activity almost the same as that of TH-2PLD as determine by kinetic analysis.     

Modulatory role of testosterone in alarm pheromone release by male rats

An alarm pheromone released from stressed conspecifics evokes behavioral and autonomic responses in rats. We have previously reported that male Wistar rats show behavioral changes including increased sniffing, walking and rearing, and decreased resting as well as exaggerated response of body temperature to a novel environment [known as stress-induced hyperthermia (SIH)] when they are exposed to an alarm pheromone released from other male rats receiving foot shocks. The purpose of the present study was to examine the role of testosterone in the production and release of the alarm pheromone using these behavioral and autonomic responses in recipient rats. Three groups of alarm pheromone donors were presented, namely, intact males, castrated males, and testosterone-implanted castrated males. The effects of the alarm pheromone on the autonomic responses did not differ among the three groups, regardless of the donor's steroidal milieu, whereas behavioral responses were altered by castrating the donor males and the effects were restored by testosterone implantation. These results suggest that the alarm pheromone released from stressed male rats can be classified into at least two categories according to the androgen dependency of their production and/or release.     

p21(Cip-1/SDI-1/WAF-1) expression via the mitogen-activated protein kinase signaling pathway in insulin-induced chondrogenic differentiation of ATDC5 cells

The embryonal carcinoma-derived cell line, ATDC5, differentiates into chondrocytes in response to insulin or insulin-like growth factor-I stimulation. In this study, we investigated the roles of mitogen-activated protein (MAP) kinases in insulin-induced chondrogenic differentiation of ATDC5 cells. Insulin-induced accumulation of glycosaminoglycan and expression of chondrogenic differentiation markers, type II collagen, type X collagen, and aggrecan mRNA were inhibited by the MEK1/2 inhibitor (U0126) and the p38 MAP kinase inhibitor (SB203580). Conversely, the JNK inhibitor (SP600125) enhanced the synthesis of glycosaminoglycan and expression of chondrogenic differentiation markers. Insulin-induced phosphorylation of ERK1/2 and JNK but not that of p38 MAP kinase. We have previously clarified that the induction of the cyclin-dependent kinase inhibitor, p21(Cip-1/SDI-1/WAF-1), is essential for chondrogenic differentiation of ATDC5 cells. To assess the relationship between the induction of p21 and MAP kinase activity, we investigated the effect of these inhibitors on insulin-induced p21 expression in ATDC5 cells. Insulin-induced accumulation of p21 mRNA and protein was inhibited by the addition of U0126 and SB203580. In contrast, SP600125 enhanced it. Inhibitory effects of U0126 or stimulatory effects of SP600125 on insulin-induced chondrogenic differentiation were observed when these inhibitors exist in the early phase of differentiation, suggesting that MEK/ERK and JNK act on early phase differentiation. SB202580, however, is necessary not only for early phase but also for late phase differentiation, indicating that p38 MAP kinase stimulates differentiation by acting during the entire period of cultivation. These results for the first time demonstrate that up-regulation of p21 expression by ERK1/2 and p38 MAP kinase is required for chondrogenesis, and that JNK acts as a suppressor of chondrogenesis by down-regulating p21 expression.     

The Neurospora Peptide:N-Glycanase Ortholog PNG1 Is Essential for Cell Polarity despite Its Lack of Enzymatic Activity

Secretory proteins are subjected to a stringent endoplasmic reticulum-based quality control system that distinguishes aberrant from correctly folded proteins. The cytoplasmic peptide:N-glycanase cleaves oligosaccharides from misfolded glycoproteins and prepares them for degradation by the 26 S proteasome. In contrast to abundant in vitro data on its enzymatic function, the in vivo relevance of peptide:N-glycanase activity remains unclear. Here we show that the PNG1 ortholog from the filamentous ascomycete Neurospora crassa is an essential protein, and its deletion results in strong polarity defects. PNG1 and its predicted binding partner RAD23 have distinct functions in N. crassa and are involved in cell wall integrity and DNA repair, respectively. Moreover, wild type PNG1 has substitutions in essential catalytic amino acids, and its deglycosylation activity is lost. These substitutions are conserved in many PNG1 orthologs of the fungal kingdom, implying a so far unrecognized enzyme-independent function of PNG1 that may only become apparent in highly polar cells such as fungal hyphae.     

Ephexin4 and EphA2 mediate cell migration through a RhoG-dependent mechanism

EphA2, a member of the Eph receptor family, is frequently overexpressed in a variety of human cancers, including breast cancers, and promotes cancer cell motility and invasion independently of its ligand ephrin stimulation. In this study, we identify Ephexin4 as a guanine nucleotide exchange factor (GEF) for RhoG that interacts with EphA2 in breast cancer cells, and knockdown and rescue experiments show that Ephexin4 acts downstream of EphA2 to promote ligand-independent breast cancer cell migration and invasion toward epidermal growth factor through activation of RhoG. The activation of RhoG recruits its effector ELMO2 and a Rac GEF Dock4 to form a complex with EphA2 at the tips of cortactin-rich protrusions in migrating breast cancer cells. In addition, the Dock4-mediated Rac activation is required for breast cancer cell migration. Our findings reveal a novel link between EphA2 and Rac activation that contributes to the cell motility and invasiveness of breast cancer cells.     

Decrease in Epstein-Barr virus-positive AIDS-related lymphoma in the era of highly active antiretroviral therapy

Recent introduction of highly active antiretroviral therapy (HAART) is reported to have reduced the incidence of lymphoma among HIV-infected individuals. A clinicopathological study was performed on 86 AIDS-related lymphoma patients who were treated in Tokyo area from 1987 to 2005. The incidence of lymphoma detected by autopsy was 27% (53 cases/198 autopsies). Diffuse large B cell lymphoma was the most predominant histological subtype throughout the period (78%). Burkitt's lymphoma (BL) increased from 2% in the pre-HAART era (before end-1997) to 13% in the HAART era, whereas incidence of BL did not vary between HAART users and non-users. Epstein-Barr virus (EBV)-positive lymphoma decreased from 88% in the pre-HAART era to 58% in the HAART era, but did not differ significantly between HAART users (73%) and non-users (74%). Nodal involvement of lymphoma increased from 14% in the pre-HAART era to 50% in the HAART era; however, central nervous system involvement decreased from 62 to 38%. Kaposi's sarcoma-associated herpesvirus infection was rare (4%) among all cases. These data suggest that HAART might play a partial role in these changes, and the alteration in immunological backgrounds, such as EBV prevalence, is suggested as another leading cause of these changes in Japanese AIDS-related lymphoma.     

Rapid construction of Drosophila RNAi transgenes using pRISE, a P-element-mediated transformation vector exploiting an in vitro recombination system

RNAi is a gene-silencing phenomenon mediated by double-stranded RNA (dsRNA) and has become a powerful tool to elucidate gene function. To accomplish rapid construction of transgenes expressing dsRNA in Drosophila, we developed a novel transformation vector, pRISE, which contains an inverted repeat of the attR1-ccdB-attR2 cassette for in vitro recombination and a pentameric GAL4 binding site for conditional expression. These features enabled us to construct RNAi transgenes without a complicated cloning scheme. In cultured cells and transgenic flies, pRISE constructs carrying dsRNA transgenes induced effective RNAi against an EGFP transgene and the endogenous white gene, respectively. These results indicate that pRISE is a convenient transformation vector for studies of multiple Drosophila genes for which functional information is lacking.     

Release of RASSF1C from the nucleus by Daxx degradation links DNA damage and SAPK/JNK activation

Stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) responds to a variety of stress stimuli and controls cell fates such as cell cycle entrance, apoptosis and senescence. Stimuli such as ultraviolet irradiation and chemical reagents that damage genomic DNA induce the activation of the SAPK/JNK signaling pathway. However, it is unclear how the signal arising in the nucleus owing to DNA damage is transmitted to SAPK/JNK in the cytoplasm. Here, we report that the nuclear components Daxx and Ras-association domain family 1C (RASSF1C) link DNA damage to SAPK/JNK activation in HeLa cells. In response to DNA damage, Daxx localized in promyelocytic leukaemia-nuclear bodies (PML-NBs) undergoes ubiquitination and degradation. RASSF1C, a tumor suppressor and newly identified binding partner of Daxx, is constitutively anchored by Daxx in PML-NBs but is released from the nucleus when Daxx is degraded. This released RASSF1C translocates to cytoplasmic microtubules and participates in the activation of SAPK/JNK. Our data define a novel mechanism by which the Daxx-RASSF1C complex in PML-NBs couples nuclear DNA damage to the cytoplasmic SAPK/JNK signaling pathway.