Cell Signaling

Flip-Flop Messenger

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Science  21 Sep 2012:
Vol. 337, Issue 6101, pp. 1434-1435
DOI: 10.1126/science.337.6101.1434-d

CD38 is a transmembrane protein present on lymphocytes that appears to function in signal transduction. It has multiple enzymatic activities, two of which cause the generation of molecules that function to regulate the release of calcium from intracellular stores [cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate (NAADP)]. Enigmatically however, the catalytic domain of CD38 has been localized to the outside of the cell. Zhao et al. used antibodies specific to the N- and C-termini of CD38 to look more closely at its orientation. They found that in multiple cell lines and in primary human peripheral blood mononuclear cells, a few percent of the cells expressed CD38 with the catalytic C-terminal portion of the protein on the inside, with some cells expressing the protein in both orientations. The authors propose that regulated expression of CD38 in its different orientations might provide a mechanism for control of its effects on intracellular signaling.

Sci. Signal. 5, ra67 (2012).

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