Cellular growth state differentially regulates enterocyte gene expression in butyrate-treated HT-29 cells.
Enterocyte differentiation occurs at the crypt-villus junction through the transcriptional activation of cell-specific genes, including the brush-border enzyme intestinal alkaline phosphatase (IAP) and the microvillar structural protein, villin. Based upon previous in vivo studies demonstrating that IAP and villin are differentially affected by alterations in epithelial growth state, we examined the regulation of these two genes in an in vitro model of enterocyte differentiation. HT-29 cells were maintained in DMEM + 10% FCS and treated with sodium butyrate to induce enterocyte differentiation. Cell count and [3H]thymidine measurements confirm that sodium butyrate causes a marked decrease in cellular growth state, consistent with the differentiation process. Northern blot analyses revealed time- and dose-dependent increases (P < 0.001) in steady-state IAP and villin mRNA levels. The increases in both IAP and villin expression were dependent upon the presence of one or more newly synthesized proteins. Post-confluence and serum starvation were used to cause cell cycle withdrawal prior to the differentiation process. As predicted from our previous in vivo data, villin expression was unaffected by changes in cellular growth state, whereas IAP expression was dramatically diminished under hypoproliferative conditions. We conclude that early withdrawal from the cell cycle alters the course of enterocyte differentiation, specifically decreasing IAP expression.
Hodin
R A
RA
Department of Surgery, Beth Israel Hospital, Harvard Medical School, Boston, MA 02215, USA.
Meng
S
S
Archer
S
S
Tang
R
R
D000469:Alkaline Phosphatase / Q000235:genetics; D002087:Butyrates / Q000494:pharmacology*; D020148:Butyric Acid; D002135:Calcium-Binding Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D019073:HT29 Cells / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors
D002087:Butyrates; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D008840:Microfilament Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; C026615:villin; D020148:Butyric Acid; D000469:Alkaline Phosphatase; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)