title: Insulin receptor isoform switching in intestinal stem cells, progenitors, differentiated lineages and tumors: evidence that IR-B limits proliferation.
abstract: Despite evidence for the impact of insulin on intestinal epithelial physiology and pathophysiology, the expression patterns, roles, and regulation of insulin receptor (IR) and IR isoforms in the intestinal epithelium are not well characterized. IR-A is thought to mediate the proliferative effects of insulin or insulin growth factors (IGFs) in fetal or cancer cells. IR-B is considered to be the metabolic receptor for insulin in specialized tissues. This study used a novel Sox9-EGFP reporter mouse that permits isolation of intestinal epithelial stem cells (IESCs), progenitors, enteroendocrine cells and differentiated lineages, the Apc(Min/+) mouse model of precancerous adenoma and normal human intestinal and colorectal cancer (CRC) cell lines. We tested the hypothesis that there is differential expression of IR-A or IR-B in stem and tumor cells versus differentiated intestinal epithelial cells (IECs) and that IR-B impacts cell proliferation. Our findings provide evidence that IR-B expression is significantly lower in highly proliferative IESCs and progenitor cells versus post-mitotic, differentiated IECs and in subconfluent and undifferentiated versus differentiated Caco-2 cells. IR-B is also reduced in Apc(Min/+) tumors and highly tumorigenic CRC cells. These differences in IR-B were accompanied by altered levels of mRNAs encoding muscleblind-like 2 (MBNL2), a known regulator of IR alternative splicing. Forced IR-B expression in subconfluent and undifferentiated Caco-2 cells reduced proliferation and increased biomarkers of differentiation. Our findings indicate that the impact of insulin on different cell types in the intestinal epithelium might differ depending on relative IR-B IR-A expression levels and provide new evidence for the roles of IR-B to limit proliferation of CRC cells.
authors.affiliation: Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Andres
authors.forename: James G
authors.initials: JG
authors.lastname: Simmons
authors.forename: Amanda T
authors.initials: AT
authors.lastname: Mah
authors.forename: M Agostina
authors.initials: MA
authors.lastname: Santoro
authors.forename: Laurianne
authors.initials: L
authors.lastname: Van Landeghem
authors.forename: P Kay
authors.initials: PK
authors.lastname: Lund
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D002454:Cell Differentiation; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000378:metabolism*; D004261:DNA Replication; D015870:Gene Expression; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D051379:Mice; D010641:Phenotype; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
chemical_list: C495270:CTNNB1 protein, human; D020033:Protein Isoforms; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D011972:Receptor, Insulin
keywords: Colon cancer; Differentiation; Insulin receptor isoform B; Intestinal stem cell; Proliferation