Scavenging of soluble and immobilized CCL21 by ACKR4 regulates peripheral dendritic cell emigration

Leukocyte homing driven by the chemokine CCL21 is pivotal for adaptive immunity because it controls dendritic cell (DC) and T cell migration through CCR7. ACKR4 scavenges CCL21 and has been shown to play an essential role in DC trafficking at the steady state and during immune responses to tumors and cutaneous inflammation. However, the mechanism by which ACKR4 regulates peripheral DC migration is unknown, and the extent to which it regulates CCL21 in steady-state skin and lymph nodes (LNs) is contested. Specifically, our previous findings that CCL21 levels are increased in LNs of ACKR4-deficient mice [I. Comerford et al., Blood 116, 4130-4140 (2010)] were refuted [M. H. Ulvmar et al., Nat. Immunol. 15, 623-630 (2014)], and no differences in CCL21 levels in steady-state skin of ACKR4-deficient mice were reported despite compromised CCR7-dependent DC egress in these animals [S. A. Bryce et al., J. Immunol. 196, 3341-3353 (2016)]. Here, we resolve these issues and reveal that two forms of CCL21, full-length immobilized and cleaved soluble CCL21, exist in steady-state barrier tissues, and both are regulated by ACKR4. Without ACKR4, extracellular CCL21 gradients in barrier sites are saturated and nonfunctional, DCs cannot home directly to lymphatic vessels, and excess soluble CCL21 from peripheral tissues pollutes downstream LNs. The results identify the mechanism by which ACKR4 controls DC migration in barrier tissues and reveal a complex mode of CCL21 regulation in vivo, which enhances understanding of functional chemokine gradient formation.

A consensus cAMP-dependent protein kinase (PK-A) site in place of the CcN motif casein kinase II site simian virus 40 large T-antigen confers PK-A-mediated regulation of nuclear import

The regulation of nuclear protein transport by phosphorylation plays a central role in gene expression in eukaryotic cells. We previously showed that nuclear import of SV40 large tumor antigen (T-ag) fusion proteins is regulated by the CcN motif, comprising phosphorylation sites for casein kinase II and the cyclin-dependent kinase cdc2, together with the nuclear localization signal. Regulation of nuclear uptake by CcN motif kinase sites also holds true for the yeast transcription factor SWI5 and the Xenopus nuclear phosphoprotein nucleoplasmin. To test directly whether a kinase site other than those of the CcN motif could regulate nuclear import of T-ag, the CcN motif casein kinase II site, which markedly increases the rate of T-ag nuclear import, was replaced by a consensus site for the cAMP-dependent protein kinase (PK-A) using site-directed mutagenesis. The resultant fusion protein could be specifically phosphorylated by PK-A in vitro and in cell extracts. Nuclear import of the fluorescently labeled protein was analyzed in the HTC rat hepatoma cell line both in vivo (microinjected cells) and in vitro (mechanically perforated cells) in the presence and the absence of cAMP and/or PK-A catalytic subunit using confocal laser scanning microscopy. In vitro PK-A-prephosphorylated protein was also tested. All results indicated that the rate of nuclear import was increased by phosphorylation at the PK-A site (2-5-fold), demonstrating that kinases other than those of the CcN motif can regulate nuclear import in response to stimulatory signals. The phosphorylation-regulated nuclear localization signal derived here represents an important first step toward developing a signal conferring inducible nuclear targeting of molecules of interest.

Relative importance of sympathetic nerves and of circulating adrenaline and vasopressin in mediating hypertension after lesions of the caudal ventrolateral medulla in the rat

Electrolytic lesions of the A1 noradrenaline cells in the caudal ventrolateral medulla cause transient hypertension and bradycardia in the conscious rat, as previously described in the rabbit. The lesions produced 100-fold increases in plasma arginine vasopressin, 40-fold increases in plasma adrenaline and fourfold increases in plasma noradrenaline levels. Absence of circulating vasopressin [homozygous diabetes insipidus rats (DI)] or circulating adrenaline (adrenalectomized rats) did not affect A1 hypertension, but sympathectomy with systemic 6-hydroxydopamine (6-OHDA) significantly attenuated A1 hypertension. A factorial experiment was performed to assess the relative contributions of these three peripheral effector mechanisms in a quantitative manner, with combined deficiencies of any two or of all three of these effector systems. Results suggest A1 hypertension in the rat to be primarily mediated through increased sympatho-adrenal activity. The largest component of hypertension (66%) results from increased sympathetic vasoconstrictor nerve activity, and a smaller part (34%) reflects the action of circulating adrenaline. Increases in vasopressin levels do not contribute to A1 hypertension, although vasopressin makes a major contribution to A1 lesion bradycardia.

Single day or single dose treatment of urinary tract infection with Co-trimoxazole

Forty-eight women with urinary tract infection due to Co-trimoxazole sensitive organisms were randomly allocated to receive either two tablets (0.96 grams) of Co-trimoxazole twice a day for one day, four tablets (1.92 grams) of Co-trimoxazole as a single dose, or, two tablets of Co-trimoxazole twice a day for seven days. The infection cure rate was comparable in each group being 82%, 87% and 81% respectively. The patients who received the single dose had a high incidence of minor side effects. Accordingly one-day treatment appears to be the treatment mode of choice. Failure to respond to single dose or single day treatment may indicate those patients requiring investigation of their urinary tract.