Phosphoregulation of K(+)-Cl(-) cotransporter 4 during changes in intracellular Cl(-) and cell volume

It has long been stated that the K(+)-Cl(-) cotransporters (KCCs) are activated during cell swelling through dephosphorylation of their cytoplasmic domains by a protein phosphatase (PP) but that other enzymes are involved by targeting this PP or the KCCs directly. To date, however, the role of signaling intermediates in KCC regulation has been deduced from indirect evidence rather than in vitro phosphorylation studies, and examined after simulation of ion transport through cell swelling or N-ethylmaleimide treatment. In this study, the oocyte expression system was used to examine the effects of changes in cell volume (C(VOL)) and intracellular [Cl(-)] ([Cl(-)](i)) on the activity and phosphorylation levels (P(LEV)) of KCC4, and determine whether these effects are mediated by PP1 or phorbol myristate acetate (PMA)-sensitive effectors. We found that (1) low [Cl(-)](i) or low C(VOL) leads to decreased activity but increased P(LEV), (2) high C(VOL) leads to increased activity but no decrease in P(LEV) and (3) calyculin A (Cal A) or PMA treatment leads to decreased activity but no increase in P(LEV). Thus, we have shown for the first time that one of the KCCs can be regulated through direct phosphorylation, that changes in [Cl(-)](i) or C(VOL) modify the activity of signaling enzymes at carrier sites, and that the effectors directly involved do not include a Cal A-sensitive PP in contrast to the widely held view. J. Cell. Physiol. 219: 787-796, 2009. (c) 2009 Wiley-Liss, Inc.

Crystal chemistry and hydrogen bonding of rustumite Ca10(Si2O7)2(SiO4)(OH)2Cl2 with variable OH, Cl, F

Three samples of the skarn mineral rustumite Ca10(Si2O7)2(SiO4)(OH)2Cl2, space group C2/c, a ≈7.6, b ≈ 18.5, c ≈ 15.5 Å, β ≈ 104°, with variable OH, Cl, F content were investigated by electron microprobe, single-crystal X-ray structure refinements, and Raman spectroscopy. “Rust1LCl” is a low chlorine rustumite Ca10(Si2O7)2(SiO4)(OH1.88F0.12)(Cl1.28,OH0.72) from skarns associated with the Rize batholith near Ikizedere, Turkey. “Rust2F” is a F-bearing rustumite Ca10(Si2O7)2(SiO4)(OH1.13F0.87) (Cl1 96OH0.04) from xenoliths in ignimbrites of the Upper Chegem Caldera, Northern Caucasus, Russia. “Rust3LClF” represents a low-Cl, F-bearing rustumite Ca10(Si2O7)2(SiO4)0.87(H4O4)0.13(OH1.01F0.99) (Cl1.00 OH1.00) from altered merwinite skarns of the Birkhin massif, Baikal Lake area, Eastern Siberia, Russia. Rustumite from Birkhin massif is characterized by a significant hydrogarnet-like or fluorine substitution at the apices of the orthosilicate group, leading to specific atomic displacements. The crystal structures including hydrogen positions have been refined from single-crystal X-ray data to R1 = 0.0205 (Rust1_LCl), R1 = 0.0295 (Rust2_F), and R1 = 0.0243 (Rust3_LCl_F), respectively. Depletion in Cl and replacement by OH is associated with smaller unit-cell dimensions. The substitution of OH by F leads to shorter hydrogen bonds O-H⋯F instead of O-H⋯OH. Raman spectra for all samples have been measured and confirm slight strengthening of the hydrogen bonds with uptake of F.This study discusses the complex crystal chemistry of the skarn mineral rustumite and may provide a wider understanding of the chemical reactions related to contact metamorphism of limestones.

Resolving Cl and SO4 Profiles in a Clay-Rich Rock Sequence

The chloride and sulfate concentration profiles in a 260 m thick clay-rich Mesozoic sediment sequence have been analyzed by various methods. Chloride data generally indicate a good consistency between different methods if anion exclusion is accounted for in leaching tests. For sulfate, however, there is an apparent inconsistency between leaching data and those obtained from the other methods, which points to the dissolution of a sulfur-bearing mineral. Traces of diagenetic gypsum seem to be a likely source, but other sulfur minerals cannot be ruled out.