| Autor: |
Ito, Akihiko, Ichiyanagi, Naoki, Ikeda, Yuki, Hagiyama, Man, Inoue, Takao, Kimura, Keiko B., Sakurai, Minami A., Hamaguchi, Kazuyuki, Murakami, Yoshinori |
| Zdroj: |
Islets; January 2012, Vol. 4 Issue: 1 p49-55, 7p |
| Abstrakt: |
Cell adhesion molecule-1 (CADM1) is a recently identified adhesion molecule of pancreatic islet α-cells that mediates nerve–α-cell interactions via trans-homophilic binding and serves anatomical units for the autonomic control of glucagon secretion. CADM1 also mediates attachment between adjacent α-cells. Since gap junctional intercellular communication (GJIC) among islet cells is essential for islet hormone secretion, we examined whether CADM1 promotes GJIC among α-cells and subsequently participates in glucagon secretion regulation. Dye transfer assays using αTC6 mouse α-cells, which endogenously express CADM1, supported this possibility; efficient cell-to-cell spread of gap junction-permeable dye was detected in clusters of αTC6 cells transfected with nonspecific, but not with CADM1-targeting, siRNA. Immunocytochemical analysis of connexin 36, a major component of the gap junction among αTC6 cells, revealed that it was localized exclusively to the cell membrane in CADM1-non-targeted αTC6 cells, but diffusely to the cytoplasm in CADM1-targeted cells. Next, we incubated CADM1-targeted and non-targeted αTC6 cells in a medium containing 1 mM glucose and 200 mM arginine for 30 min to induce glucagon secretion, and found that the targeted cells secreted three times more glucagon than did the non-targeted. We conducted similar experiments using pancreatic islets that were freshly isolated from wild-type and CADM1-knockout mice, and expressed glucagon secretion as ratios relative to baseline values. The increase in ratio was larger in CADM1-knockout islets than in wild-type islets. These results suggest that CADM1 may serve as a volume limiter of glucagon secretion by sustaining α-cell attachment necessary for efficient GJIC. |
| Databáze: |
Supplemental Index |
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