The function of interleukin 5 receptor alpha and beta sub- units in the signaling pathway

• Main Authors: Shin Yi Lin, 林幸宜
• Other Authors: Pao Wei Liu, Jong Yang Yen
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/86307437626465146222

碩士 === 輔仁大學 === 生物學研究所 === 83 === The patients with asthma usually follow with eosino- philia. The main cytokine activates eosinophils is inter- leukin 5 ( IL-5 ) and the signal is transduced through its receptor. There are two receptor subuits involved in the signal transduction : alpha chain is a ligand specific subunit with only low affinity without cooperation to beta chain; beta chain does not bind to ligand by itself but is required for high affinity binding site. Thus, these two subunits play important roles in the signal transduction of IL-5 in eosinophils. To understand the functions of alpha and beta subunits in the signaling pathway, a murine IL-3- dependent pro-B cell line, Ba/F3 was used as a recipient. The alpha and beta subunits of IL-5 receptor were introduced into Ba/F3 cells and monitored the events generated by these receptor subunits. In our observation, introducing the beta chain into Ba/F3 is sufficient to accelerate the cell death either in the absence of cytokine or the presence of hIL-5. Overexpression of alpha subunit confers Ba/F3 cells the ability to grow in hIL-5 containing medium which is pro- portional to the expression level of receptor alpha chain. Co- transfection of alpha and beta chain confers recipient a hIL-5- dependent growth, however also an accelerated death in the absence of hIL-5. ED50 of hIL-5 in Ba/F3ab cells is lower than that in Ba/F3a cells which indicates that human alpha chain is able to form a low-affinity functional receptor with murine beta chain. Taking all data together, we propose a model where an unoccupied beta chain constant- ly sending death signal and when accompanied by alpha chain ,the alpha-beta complex subuits sending mitogenesis signal.