TY - JOUR
T1 - Expression of CD38 with intracellular enzymatic activity
T2 - A possible explanation for the insulin release induced by intracellular cADPR
AU - Ohta, Yasuhiko
AU - Kitanaka, Akira
AU - Mihara, Keichiro
AU - Imataki, Osamu
AU - Ohnishi, Hiroaki
AU - Tanaka, Terukazu
AU - Taminato, Tomohiko
AU - Kubota, Yoshitsugu
PY - 2011/6
Y1 - 2011/6
N2 - CD38 is a transmembrane glycoprotein expressed in multiple cell types, including pancreatic β cells. It can serve as an enzyme that catalyzes the metabolism of two different Ca2+-mobilizing compounds, cyclic adenosine diphosphoribose (cADPR) and nicotinic acid adenine dinucleotide phosphate. One of these metabolites, cADPR, is known to be involved in glucose-induced insulin secretion from pancreatic β cells. Although the essential role of CD38 for endogenous cADPR synthesis has been established, the relationship between the proposed extracellular enzymatic activity of CD38 and the intracellular Ca2+ modulation caused by the intracellular cADPR accumulation has not yet been fully explained. For a better understanding of the role of CD38 in the insulin secretion machinery, analysis of the intracellular localization of this molecule in pancreatic β cells is essential. In an attempt to provide a method to probe the N-terminal and C-terminal of CD38 separately, we generated an insulin-secreting MIN6 murine pancreatic β cell line expressing a human CD38 bearing an N-terminal FLAG epitope tag. We found a weak but consistent expression of the FLAG epitope outside of the cells, indicating the presence of a small amount of CD38 with cytoplasmic enzymatic activity. MIN6 cells transfected with human CD38 exhibited increased glucose-induced insulin release. In addition, anti-FLAG cross-linking further enhanced the insulin release, suggesting that the N-terminal of CD38 expressed on the cell surface functions as a receptor for an unknown ligand and triggers positive signals for insulin secretion.
AB - CD38 is a transmembrane glycoprotein expressed in multiple cell types, including pancreatic β cells. It can serve as an enzyme that catalyzes the metabolism of two different Ca2+-mobilizing compounds, cyclic adenosine diphosphoribose (cADPR) and nicotinic acid adenine dinucleotide phosphate. One of these metabolites, cADPR, is known to be involved in glucose-induced insulin secretion from pancreatic β cells. Although the essential role of CD38 for endogenous cADPR synthesis has been established, the relationship between the proposed extracellular enzymatic activity of CD38 and the intracellular Ca2+ modulation caused by the intracellular cADPR accumulation has not yet been fully explained. For a better understanding of the role of CD38 in the insulin secretion machinery, analysis of the intracellular localization of this molecule in pancreatic β cells is essential. In an attempt to provide a method to probe the N-terminal and C-terminal of CD38 separately, we generated an insulin-secreting MIN6 murine pancreatic β cell line expressing a human CD38 bearing an N-terminal FLAG epitope tag. We found a weak but consistent expression of the FLAG epitope outside of the cells, indicating the presence of a small amount of CD38 with cytoplasmic enzymatic activity. MIN6 cells transfected with human CD38 exhibited increased glucose-induced insulin release. In addition, anti-FLAG cross-linking further enhanced the insulin release, suggesting that the N-terminal of CD38 expressed on the cell surface functions as a receptor for an unknown ligand and triggers positive signals for insulin secretion.
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U2 - 10.1007/s11010-011-0765-x
DO - 10.1007/s11010-011-0765-x
M3 - Article
C2 - 21387169
AN - SCOPUS:79959264613
SN - 0300-8177
VL - 352
SP - 293
EP - 299
JO - Enzymologia
JF - Enzymologia
IS - 1-2
ER -