Functional MYO5B Loss Alters Lipid Metabolic Pathways in Intestinal Progenitor Cells

Abstract

Background and Aims: Differentiation of intestinal epithelial cells involves cell division inhibition, cell lineage choice, and brush border elaboration. Myosin Vb (MYO5B) is a motor protein that is critical for cell polarization and membrane protein trafficking in intestinal epithelial cells and its deficiency causes both hyperproliferation and microvillus defects. Recently, we reported that a bioactive phospholipid, lysophosphatidic acid (LPA), can promote cell differentiation and nutrient absorption in tamoxifen‐induced MYO5B knockout mice in vivo and in enteroids. Our RNA‐sequencing data with KEGG pathway and GO enrichment analysis indicated that MYO5B loss disrupts stem cell characteristics, cell lineage differentiation, and energy metabolic pathways. We hypothesize that the alteration of metabolic pathways in progenitor cells causes the disruption of stem cell function.Methods: Adult Villin‐CreERT2;Myo5bflox/flox or littermate control (Myo5bflox/flox) mice received a single dose of tamoxifen and the intestinal tissues were analyzed 4 days after the tamoxifen injection. Fresh frozen sections of jejunum were analyzed by imaging mass spectrometry (IMS). Immunostaining for key metabolic enzymes were utilized to support the RNA‐seq and IMS observations.Results: Using RNA‐sequencing, MYO5B deficient epithelial cells showed significant decreases in transcripts for enzymes that mediate fatty acid ß‐oxidation compared to control mouse jejunum. Instead, Acsl3, Acat2, and Hmgcs2 were significantly upregulated, proteins that are important for lipogenesis, cholesterol ester synthesis, and ketogenesis, respectively. Consistent with these results, IMS demonstrated that MYO5B deficient tissues accumulated long‐chain fatty acids, phosphatidylinositol, cholesterol derivatives, and nucleotide products in the mucosa (Figure 1). Immunostaining signals of HMGCS2 in control mouse jejunum is limited to the crypt stem cells, whereas MYO5B‐deficient intestine showed expanded HMGCS2 expression in the proliferative cell zone. Interestingly, systemic LPA treatment in MYO5B‐deficient mice further increased the expression of HMGCS2 in both proliferating and differentiated epithelial cells (Figure 2). These observations suggest that MYO5B loss induces a starvation‐like phenotype in proliferative epithelial cells and that LPA treatment increased ketone body production as alternative energy fuels, resulting in the promotion of epithelial cell differentiation.Conclusion: MYO5B loss impairs fatty acid oxidation in the intestinal progenitor cells, which likely leads to cell differentiation deficits. Alteration of metabolic pathways might be a therapeutic target for epithelial disfunction seen in diarrheal diseases.