Mouse anti-Human KCNN4 polyclonal antibody

Sandle GI, Rajendran VM. Cyclic AMP-induced K+ secretion occurs independently of Cl- secretion in rat distal colon. Am J Physiol Cell Physiol 303: C328-C333, 2012. First published May 30, 2012; doi: 10.1152/ajpcell.00099.2012.-cAMP induces both active Cl- and active K+ secretion in mammalian colon. It is generally assumed that a mechanism for K+ exit is essential to maintain cells in the hyperpolarized state, thus favoring a sustained Cl- secretion. Both Kcnn4c and Kcnma1 channels are located in colon, and this study addressed the questions of whether Kcnn4c and/or Kcnma1 channels mediate cAMP-induced K+ secretion and whether cAMP-induced K+ secretion provides the driving force for Cl- secretion. Forskolin (FSK)-enhanced short-circuit current (indicator of net electrogenic ion transport) and K+ fluxes were measured simultaneously in colonic mucosa under voltage-clamp conditions. Mucosal Na+ orthovanadate (P-type ATPase inhibitor) inhibited active K+ absorption normally present in rat distal colon. In the presence of mucosal Na+ orthovanadate, serosal FSK induced both K+ and Cl- secretion. FSK-induced K+ secretion was 1) not inhibited by either mucosal or serosal 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34; a Kcnn4 channel blocker), 2) inhibited (92%) by mucosal iberiotoxin (Kcnma1 channel blocker), and 3) not affected by mucosal cystic fibrosis transmembrane conductance regulator inhibitor (CFTRinh-172). By contrast, FSK-induced Cl- secretion was 1) completely inhibited by serosal TRAM-34, 2) not inhibited by either mucosal or serosal iberiotoxin, and 3) completely inhibited by mucosal CFTRinh-172. These results indicate that cAMP-induced colonic K+ secretion is mediated via Kcnma1 channels located in the apical membrane and most likely contributes to stool K+ losses in secretory diarrhea. On the other hand, cAMP-induced colonic Cl- secretion requires the activity of Kcnn4b channels located in the basolateral membrane and is not dependent on the concurrent activation of apical Kcnma1 channels.

We describe the clinical, hematologic and genetic characteristics of a retrospective series of 126 subjects from 64 families with hereditary xerocytosis. Twelve patients from six families carried a KCNN4 mutation, five had the recurrent p.Arg352His mutation and one had a new deletion at the exon 7-intron 7 junction. Forty-nine families carried a PIEZO1 mutation, which was a known recurrent mutation in only one-third of the cases and private sequence variation in others; 12 new probably pathogenic missense mutations were identified. The two dominant features leading to diagnosis were hemolysis that persisted after splenectomy and hyperferritinemia, with an inconstant correlation with liver iron content assessed by magnetic resonance imaging. PIEZO1-hereditary xerocytosis was characterized by compensated hemolysis in most cases, perinatal edema of heterogeneous severity in more than 20% of families and a major risk of post-splenectomy thrombotic events, including a high frequency of portal thrombosis. In KCNN4-related disease, the main symptoms were more severe anemia, hemolysis and iron overload, with no clear sign of red cell dehydration; therefore, this disorder would be better described as a 'Gardos channelopathy'. These data on the largest series to date indicate that PIEZO1-hereditary xerocytosis and Gardos channelopathy are not the same disease although they share hemolysis, a high rate of iron overload and inefficient splenectomy. They demonstrate the high variability in clinical expression as well as genetic bases of PIEZO1-hereditary xerocytosis. These results will help to improve the diagnosis of hereditary xerocytosis and to provide recommendations on the clinical management in terms of splenectomy, iron overload and pregnancy follow-up.