Suppression of the alpha-isoform of class II phosphoinositide 3-kinase gene expression leads to apoptotic cell death.
Phosphoinositide 3-kinases (PI3Ks) have known to be key enzymes activating intracellular signaling molecules when a number of growth factors bind to their cell surface receptors. PI3Ks are divided into three classes (I, II, and III) and enzymes of each class have different tissue-specificities and physiological functions. Class II PI3Ks consist of three isoforms (alpha,beta,gamma). Although the alpha-isoform (PI3K-C2alpha) is considered ubiquitous and preferentially activated by insulin rather than the beta-isoform, the physiological significance of PI3K-C2alpha is poorly understood. The present study aimed to determine whether PI3K-C2alpha is associated with the suppression of apoptotic cell death. Different sense- and antisense oligonucleotides (ODNs) were synthesized based on the sequence of C2 domain of PI3K-C2alpha gene. Transfection of CHO-IR cells with two different antisense ODNs clearly reduced the protein content as well as mRNA levels of PI3K-C2alpha whereas neither the nonspecific mock- nor sense ODNs affected. The decrease of PI3K-C2alpha gene expression was paralleled by cellular changes indicating apoptotic cell death such as nuclear condensation, formation of apoptotic bodies, and DNA fragmentation. PI3K-C2alpha mRNA levels were also reduced when cells were incubated in growth factor-deficient medium. Supplementing growth factors (serum or insulin) into medium lead to an increase of PI3K-C2alpha mRNA levels. This finding strongly suggests that PI3K-C2alpha is a crucial survival factor.
Kang
Shinhae
S
Technology Innovation Center, Cheju National University, Jeju, Jeju 690-756, Republic of Korea.
Song
Jihoon
J
Kang
Jihoon
J
Kang
Heekyoung
H
Lee
Daeho
D
Lee
Youngki
Y
Park
Deokbae
D
D000818:Animals; D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D016466:CHO Cells; D002460:Cell Line; D002470:Cell Survival; D006224:Cricetinae; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D009841:Oligonucleotides / Q000737:chemistry; D016376:Oligonucleotides, Antisense / Q000737:chemistry; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection
D016895:Culture Media, Serum-Free; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D020033:Protein Isoforms; D012333:RNA, Messenger; D019869:Phosphatidylinositol 3-Kinases