B2

Intramembranous processing by gamma-secretase regulates reverse signaling of ephrin-B2 in migration of microglia.[Pubmed:28370426]

Glia. 2017 Jul;65(7):1103-1118.

The Eph-ephrin system plays pivotal roles in cell adhesion and migration. The receptor-like functions of the ephrin ligands allow the regulation of intracellular processes via reverse signaling. gamma-Secretase mediated processing of ephrin-B has previously been linked to activation of Src, a kinase crucial for focal adhesion and podosome phosphorylation. Here, we analyzed the role of gamma-secretase in the stimulation of reverse ephrin-B2 signaling in the migration of mouse embryonic stem cell derived microglia. The proteolytic generation of the ephrin-B2 intracellular domain (ICD) by gamma-secretase stimulates Src and focal adhesion kinase (FAK). Inhibition of gamma-secretase decreased the phosphorylation of Src and FAK, and reduced cell motility. These effects were associated with enlargement of the podosomal surface. Interestingly, expression of ephrin-B2 ICD could rescue these effects, indicating that this proteolytic fragment mediates the activation of Src and FAK, and thereby regulates podosomal dynamics in microglial cells. Together, these results identify gamma-secretase as well as ephrin-B2 as regulators of microglial migration.

Bradykinin/B2 receptor activation regulates renin in M-1 cells via protein kinase C and nitric oxide.[Pubmed:28373410]

Physiol Rep. 2017 Apr;5(7). pii: 5/7/e13211.

In the collecting duct (CD), the interactions of renin angiotensin system (RAS) and kallikrein-kinin system (KKS) modulate Na(+) reabsorption, volume homeostasis, and blood pressure. In this study, we used a mouse kidney cortical CD cell line (M-1 cells) to test the hypothesis that in the CD, the activation of bradykinin B2 receptor (B2R) increases renin synthesis and release. Physiological concentrations of bradykinin (BK) treatment of M-1 cells increased renin mRNA and prorenin and renin protein contents in a dose-dependent manner and increased threefold renin content in the cell culture media. These effects were mediated by protein kinase C (PKC) independently of protein kinase A (PKA) because B2R antagonism with Icatibant and PKC inhibition with calphostin C, prevented these responses, but PKA inhibition with H89 did not modify the effects elicited by the B2R activation. BK-dependent stimulation of renin gene expression in CD cells also involved nitric oxide (NO) pathway because increased cGMP levels and inhibition of NO synthase with L-NAME prevented it. Complementary renin immunohistochemical studies performed in kidneys from mice with conventional B2R knockout and conditional B2R knockout in the CD, showed marked decreased renin immunoreactivity in CD, regardless of the renin presence in juxtaglomerular cells in the knockout mice. These results indicate that the activation of B2R increases renin synthesis and release by the CD cells through PKC stimulation and NO release, which support further the interactions between the RAS and KKS.

Infrared Multiple-Photon Dissociation Action Spectroscopy of the b2(+) Ion from PPG: Evidence of Third Residue Affecting b2(+) Fragment Structure.[Pubmed:28374317]

J Am Soc Mass Spectrom. 2017 Jul;28(7):1482-1488.

Infrared multiple-photon dissociation (IRMPD) action spectroscopy was performed on the B2(+) fragment ion from the protonated PPG tripeptide. Comparison of the experimental infrared spectrum with computed spectra for both oxazolone and diketopiperazine structures indicates that the majority of the fragment ion population has an oxazolone structure with the remainder having a diketopiperazine structure. This result is in contrast with a recent study of the IRMPD action spectrum of the PP B2(+) fragment ion from PPP, which was found to be nearly 100% diketopiperazine (Martens et al. Int. J. Mass Spectrom. 2015, 377, 179). The diketopiperazine B2(+) ion is thermodynamically more stable than the oxazolone but normally requires a trans/cis peptide bond isomerization in the dissociating peptide. Martens et al. showed through IRMPD action spectroscopy that the PPP precursor ion was in a conformation in which the first peptide bond is already in the cis conformation and thus it was energetically favorable to form the thermodynamically-favored diketopiperazine B2(+) ion. In the present case, solution-phase NMR spectroscopy and gas-phase IRMPD action spectroscopy show that the PPG precursor ion has its first amide bond in a trans configuration suggesting that the third residue is playing an important role in both the structure of the peptide and the associated ring-closure barriers for oxazolone and diketopiperazine formation. Graphical Abstract .

Spread of CTX-Type Extended-Spectrum beta-Lactamase-Producing Escherichia coli Isolates of Epidemic Clone B2-O25-ST131 Among Dogs and Cats in Japan.[Pubmed:28380311]

Microb Drug Resist. 2017 Dec;23(8):1059-1066.

This study was performed to investigate the carriage rates of CTX-M-type extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli among ill companion animals in Japan. Among the 178 nonrepetitive E. coli isolates, including 131 from dogs and 47 from cats, collected between September and November 2015, 42 (23.6%) isolates from 29 dogs and 13 cats were identified as ESBL producers. The antimicrobial susceptibility, O serotype, phylogenetic group, beta-lactamase genotype, plasmid replicon type, and sequence type (ST) of each isolate were analyzed. The major ESBL types were CTX-M-14 (26.8%), CTX-M-15 (24.4%), CTX-M-27 (19.5%), and CTX-M-55 (19.5%); predominant replicon types of blaCTX-M-carrying plasmid were IncF group and IncI1-Igamma. The most prevalent STs were ST131 (n = 15, 35.7%), followed by ST38, ST10, and ST410. The 15 isolates of ST131 belonged to B2-O25. E. coli B2-O25-ST131 isolates harboring blaCTX-M-15 or blaCTX-M-27 were resistant to ceftazidime and ciprofloxacin. In particular, CTX-M-15 producers showed multidrug resistance. Our results demonstrated that the CTX-M-producing pandemic E. coli clone B2-O25-ST131 has already spread in Japanese companion animals as well. Moreover, the similarity of genotypes, serotypes, phylogenetic groups, and STs of the isolates from companion animals to those from humans suggested probable transmission of resistant bacteria between pets and humans.