Abstract
α‐Amylase, which plays an essential role in starch degradation, is expressed mainly in the pancreas and salivary glands. Human α‐amylase is also detected in other tissues, but it is unclear whether the α‐amylase is endogenously expressed in each tissue or mixed exogenously with one expressed by the pancreas or salivary glands. Furthermore, the biological significance of these α‐amylases detected in tissues other than the pancreas and salivary glands has not been elucidated. We discovered that human α‐amylase is expressed in intestinal epithelial cells and analyzed the effects of suppressing α‐amylase expression. α‐Amylase was found to be expressed at the second‐highest messenger RNA level in the duodenum in human normal tissues after the pancreas. α‐Amylase was detected in the cell extract of Caco‐2 intestinal epithelial cells but not secreted into the culture medium. The amount of α‐amylase expressed increased depending on the length of the culture of Caco‐2 cells, suggesting that α‐amylase is expressed in small intestine epithelial cells rather than the colon because the cells differentiate spontaneously upon reaching confluence in culture to exhibit the characteristics of small intestinal epithelial cells rather than colon cells. The α‐amylase expressed in Caco‐2 cells had enzymatic activity and was identified as AMY2B, one of the two isoforms of pancreatic α‐amylase. The suppression of α‐amylase expression by small interfering RNA inhibited cell differentiation and proliferation. These results demonstrate for the first time that α‐amylase is expressed in human intestinal epithelial cells and affects cell proliferation and differentiation. This α‐amylase may induce the proliferation and differentiation of small intestine epithelial cells, supporting a rapid turnover of cells to maintain a healthy intestinal lumen.
Highlights
In the cell seeding at 2.0 × 105 cells/cm[2], the expressions of all differentiation makers were clearly inhibited by the suppression of α‐amylase expression. These results show that the suppression of α‐amylase expression inhibits the expression of differentiation markers, suggesting that the α‐amylase expressed in the cell is necessary to induce cell differentiation
We examined whether α‐amylase is expressed in normal human tissues and the intestinal epithelial cell Caco‐2. α‐Amylase was found to be expressed at the highest messenger RNA (mRNA) level in the duodenum in human normal tissues after the pancreas (Figure 1)
We found that active α‐amylase is expressed in Caco‐2 cells and that the expression increased depending on the culture durations of the cells by using real‐time PCR, Western blot analysis, enzyme activity assays, and confocal microscopic images for α‐amylase (Figures 2-4)
Summary
Α‐Amylase (EC 3.2.1.1) is a digestive enzyme that catalyzes the hydrolysis of internal α‐1,4‐glycosidic bonds of starch into smaller maltooligosaccharides. Α‐Amylases are detected in in pancreas and salivary glands and in urine and blood.[6] α‐Amylase is detected in rat liver, intestine, stomach, testis, and skeletal muscle as messenger RNA (mRNA) expression and starch degrading activity.[7] Human α‐amylases have been detected in normal liver and thyroid tissues by reverse transcription polymerase chain reaction (RT‐PCR), assays of amylase activity using a starch method, histochemical analyses, and electrophoretic analysis.[8,9,10] There are three α‐amylase genes, AMY1, AMY2A, and AMY2B, in a cluster on chromosome 1 P21. The human α‐amylases detected in liver and thyroid tissues are AMY2B and AMY1, respectively.[8,10] Recently, it was reported that active α‐amylase is expressed in the human brain and that its isotypes are AMY1A and AMY2A.13. To determine the biological significance of α‐amylase expression in small intestinal epithelial cells, we analyzed the effects of suppressing α‐amylase expression
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
