Gros L, Bréant B, Duchene B, Leroy C, Fauconnier G, Bataille D, Virsolvy A
INSERM U376, CHU Arnaud-de-Villeneuve, Montpellier, France.
Diabetologia. 2002 May;45(5):703-10. doi: 10.1007/s00125-002-0794-9. Epub 2002 Apr 3.
AIMS/HYPOTHESIS: alpha-Endosulphine, a protein that belongs to the cAMP-regulated-phosphoprotein family, has been reported to modulate insulin secretion in vitro through interaction with the pancreatic beta-cell ATP-sensitive potassium (K(ATP)) channel. In this study, we analysed the tissue distribution of alpha-endosulphine and determined its pancreatic cellular localization.
Quantitative tissue distribution of alpha-endosulphine was studied by RIA on tissue extracts and cellular/subcellular localization was done using immunocytochemistry, morphometry and western blot analysis. alpha-Endosulphine and somatostatin release from RINT-3 somatostatin-secreting cells was quantified by RIA.
alpha-Endosulphine, concentrated particularly in the central nervous system, was also detected in a wide variety of tissues including the pancreas. Immunohistochemistry analysis of adult rat pancreatic sections showed that alpha-endosulphine localized in somatostatin delta cells, where its expression increased during post-natal development. Immunoreactive cells were detected from foetal age E19, and the number of somatostatin cells co-expressing alpha-endosulphine increased with developmental age from E19 until adult. alpha-Endosulphine, highly expressed in the cytoplasm of RINT3 somatostatin-secreting cell line, was recovered in the particulate fraction of RINT3 cell extracts but was not co-secreted with somatostatin.
CONCLUSION/INTERPRETATION: alpha-Endosulphine is expressed in all tissues tested including pancreas and is also detected in plasma. Pancreatic alpha-endosulphine is specifically localized in somatostatin delta cells. This cytosolic protein is not co-secreted with somatostatin and could be physically associated with particulate components of the cells. These findings are not in favour of an endocrine/paracrine effect of alpha-endosulphine on the beta-cell K(ATP) channel.
目的/假设：α-内硫磷是一种属于环磷酸腺苷调节磷蛋白家族的蛋白质，据报道它在体外通过与胰腺β细胞的三磷酸腺苷敏感性钾（K(ATP)）通道相互作用来调节胰岛素分泌。在本研究中，我们分析了α-内硫磷的组织分布并确定了其在胰腺细胞中的定位。
通过放射免疫分析法（RIA）研究α-内硫磷在组织提取物中的定量组织分布，并使用免疫细胞化学、形态计量学和蛋白质免疫印迹分析确定其细胞/亚细胞定位。通过RIA对RINT-3生长抑素分泌细胞释放的α-内硫磷和生长抑素进行定量。
α-内硫磷特别集中于中枢神经系统，在包括胰腺在内的多种组织中也可检测到。对成年大鼠胰腺切片的免疫组织化学分析表明，α-内硫磷定位于生长抑素δ细胞，其表达在出生后发育过程中增加。从胚胎第19天（E19）开始检测到免疫反应性细胞，并且共表达α-内硫磷的生长抑素细胞数量从E19到成年随着发育年龄的增加而增加。α-内硫磷在RINT3生长抑素分泌细胞系的细胞质中高度表达，在RINT3细胞提取物的颗粒部分中可检测到，但不与生长抑素共同分泌。
结论/解读：α-内硫磷在所检测的所有组织（包括胰腺）中均有表达，在血浆中也可检测到。胰腺α-内硫磷特异性定位于生长抑素δ细胞。这种胞质蛋白不与生长抑素共同分泌，可能与细胞的颗粒成分存在物理关联。这些发现不支持α-内硫磷对β细胞K(ATP)通道具有内分泌/旁分泌作用的观点。
