Diverging Mechanisms of Activation of Chemokine Receptors Revealed by Novel Chemokine Agonists

CXCL8/interleukin-8 is a pro-inflammatory chemokine that triggers pleiotropic responses, including inflammation, angiogenesis, wound healing and tumorigenesis. We engineered the first selective CXCR1 agonists on the basis of residue substitutions in the conserved ELR triad and CXC motif of CXCL8. Our data reveal that the molecular mechanisms of activation of CXCR1 and CXCR2 are distinct: the N-loop of CXCL8 is the major determinant for CXCR1 activation, whereas the N-terminus of CXCL8 (ELR and CXC) is essential for CXCR2 activation. We also found that activation of CXCR1 cross-desensitized CXCR2 responses in human neutrophils co-expressing both receptors, indicating that these novel CXCR1 agonists represent a new class of anti-inflammatory agents. Further, these selective CXCR1 agonists will aid at elucidating the functional significance of CXCR1 in vivo under pathophysiological conditions

Lattice instability and elastic dispersion due to the rattling motion in the type-I clathrate Ba_8Ga_<16>Sn_<30>

To investigate the off-center rattling motion and its charge-carrier dependence in type-I clathrate compounds, we carried out ultrasonic measurements on type-I Ba8Ga16Sn30 and a reference compound, K8Ga8Sn38. We found elastic softening of C44 originating from a lattice instability due to the off-center rattling motion of Ba atom in Ba8Ga16Sn30. Elastic softening below 1 K suggests that the lattice instability remains at very low temperatures. We also found ultrasonic dispersion which has no mode selectivity. No-mode-selective ultrasonic dispersion in Ba8Ga16Sn30 would be caused by a strong electron-phonon coupling. No charge-carrier dependence is observed between n-type and p-type Ba8Ga16Sn30. The significant softening on the bulk modulus in Ba8Ga16Sn30 contrasts to the continuous hardening in K8Ga8Sn38, indicating the central role of the rattling motion in the softening

Structure of an Engineered β-Lactamase Maltose Binding Protein Fusion Protein: Insights into Heterotropic Allosteric Regulation

Engineering novel allostery into existing proteins is a challenging endeavor to obtain novel sensors, therapeutic proteins, or modulate metabolic and cellular processes. The RG13 protein achieves such allostery by inserting a circularly permuted TEM-1 β-lactamase gene into the maltose binding protein (MBP). RG13 is positively regulated by maltose yet is, serendipitously, inhibited by Zn2+ at low µM concentration. To probe the structure and allostery of RG13, we crystallized RG13 in the presence of mM Zn2+ concentration and determined its structure. The structure reveals that the MBP and TEM-1 domains are in close proximity connected via two linkers and a zinc ion bridging both domains. By bridging both TEM-1 and MBP, Zn2+ acts to “twist tie” the linkers thereby partially dislodging a linker between the two domains from its original catalytically productive position in TEM-1. This linker 1 contains residues normally part of the TEM-1 active site including the critical β3 and β4 strands important for activity. Mutagenesis of residues comprising the crystallographically observed Zn2+ site only slightly affected Zn2+ inhibition 2- to 4-fold. Combined with previous mutagenesis results we therefore hypothesize the presence of two or more inter-domain mutually exclusive inhibitory Zn2+ sites. Mutagenesis and molecular modeling of an intact TEM-1 domain near MBP within the RG13 framework indicated a close surface proximity of the two domains with maltose switching being critically dependent on MBP linker anchoring residues and linker length. Structural analysis indicated that the linker attachment sites on MBP are at a site that, upon maltose binding, harbors both the largest local Cα distance changes and displays surface curvature changes, from concave to relatively flat becoming thus less sterically intrusive. Maltose activation and zinc inhibition of RG13 are hypothesized to have opposite effects on productive relaxation of the TEM-1 β3 linker region via steric and/or linker juxtapositioning mechanisms

209 A Review of Intravaginal Ejaculatory Dysfunction and Unconsummated Marriage Cases in the Outpatient Clinic for Male Infertility at the University of Tsukuba Hospital

ABSTRACT Introduction Male infertility can be classified into three categories of causes: testicular factors, seminal tract obstruction, and sexual disorders. Sexual disorders, in particular, have been increasing in recent years, as people now marry later in life, and lifestyles have become more diverse. This study focused on erectile dysfunction (ED) and ejaculation dysfunction (EjD) because they are direct causes of sexual disorders and infertility. The most serious sexual disorders are intravaginal ejaculation dysfunction (IVEjD), which indicates a lack of ability to ejaculate during sexual intercourse, and unconsummated marriage (UM), which means no experience of sexual intercourse after marriage. In this study, we reviewed the actual statuses of IVEjD and UM in male infertility patients who were consulted at our clinic. Objective To examine the characteristics of IVEjD and UM by comparing them with other male infertility patients. Methods This study was approved by the relevant ethical review board. We obtained data on 83 male infertility patients diagnosed from 2018–2020 at our clinic. We extracted information on IVEjD and UM patients, which were defined as serious sexual disorders (SSD). We analyzed the factors of SSD cases related to infertility. Results Of 83 male infertility cases, 26 cases had either ED or EjD. We found nine SSD cases; seven cases had IVEjD, and two cases had UM. The mean age was 38.8 years (IQR: 30–50), and the mean age of the wives was 33.6 years (IQR: 2–43). All SSD cases had never had ejaculatory intercourse with a woman including their wives. Seven cases possibly had ED or EjD, but all SSDs were able to ejaculate by masturbation. One case had premature ejaculation, and six cases had delayed ejaculation during masturbation. Three cases had poor semen findings (oligozoospermia or asthenozoospermia), one case had an organic abnormality (after phimosis surgery), and one case had active depression, but there were no abnormalities in the testicular volume or endocrine findings. The causes of SSDs were inappropriate methods of masturbation in three cases (push method in two cases, strong grip in one case), a lack of sexual experience in two cases, and sexual aversion in one case. In three cases, the wives were able to conceive, but all had undergone fertility treatments without sexual intercourse. Conclusion In this study, 31.3% of male infertility patients had sexual disorders, which is higher than the figure in the national survey. In addition, 10.8% of men had never had sexual intercourse with ejaculation in their lives, and even if we consider the fact that these are patients who visit specialized outpatient clinics, it is clear that there are more patients suffering from SSD than expected. Although sexual disorders can be caused by physical abnormalities such as neurological disorders, vascular disorders, and endocrine disorders, all nine cases examined in this study were able to ejaculate by masturbation, suggesting that lifestyle and psychological problems are the major factors of infertility. Given the difficulty in providing medical interventions for these factors, only a small percentage of cases with severe sexual dysfunction resulted in pregnancy, suggesting the difficulty involved in treating sexual dysfunctions. Disclosure Work supported by industry: no. </jats:sec