= K. Fushimi
{c}
<K. Fushimi> is the first author of the 1993 study that cloned and functionally tested the kidney water channel now known as <aquaporin-2>. The team localized it to the <collecting duct> and expressed its sequence in <Xenopus> <oocytes>, connecting a candidate <membrane protein> to measured water transport.<Cloning and expression of apical membrane water channel of rat kidney collecting tubule by K. Fushimi and others>[byline and abstract, localization and functional expression]{ref}
A 1997 first-authored study tested how that channel reaches the <cell membrane>. The investigators replaced <serine>256 with <alanine> and compared the resulting protein with the normal sequence in cultured cells. A stopped-flow light-scattering assay measured osmotic water permeability, while surface labeling assessed membrane localization. <cAMP> stimulation increased permeability by about $85\%$ for the normal construct but only about $8\%$ for the altered construct in the reported experiments.<Phosphorylation of serine 256 is required for cAMP-dependent regulatory exocytosis of the aquaporin-2 water channel by K. Fushimi and others>[abstract, S256A comparison and measured cAMP responses]{ref}
The comparison links <phosphorylation> at a defined amino-acid position to regulated <exocytosis> and membrane water transport. It also separates two questions: can a protein transport water, and can a cell adjust how much of that protein is present at its surface?
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