Stem cell antigen‐1 localizes to lipid microdomains and associates with insulin degrading enzyme in skeletal myoblasts

Abstract

Stem cell antigen-1 (Sca-1, Ly6A/E) is a glycosylphosphotidylinositol-anchored protein that identifies many tissue progenitor cells. We originally identified Sca-1 as a marker of myogenic precursor cells and subsequently demonstrated that Sca-1 regulates proliferation of activated myoblasts, suggesting an important role for Sca-1 in skeletal muscle homeostasis. Beyond its functional role in regulating proliferation, however, little is known about the mechanism(s) that drive Sca-1-mediated events. We now report that lipid microdomain organization is essential for normal myogenic differentiation, and that Sca-1 constitutively localizes to these domains during myoblast proliferation and differentiation. We also demonstrate that Sca-1 associates with insulin degrading enzyme (IDE), a catalytic protein responsible for the cleavage of mitogenic peptides, in differentiating myoblasts. We show that chemical inhibition of IDE as well as RNAi knockdown of IDE mRNA recapitulates the phenotype of Sca-1 interference, that is, sustained myoblast proliferation and delayed myogenic differentiation. These findings identify the first signaling protein that physically and functionally associates with Sca-1 in myogenic precursor cells, and suggest a potential pathway for Sca-1-mediated signaling. Future efforts to manipulate this pathway may lead to new strategies for augmenting the myogenic proliferative response, and ultimately muscle repair.

Diet-Induced Obesity in Stem Cell Antigen-1 KO Mice

“…Sca-1 has been implicated as a stem cell biomarker in multiple tissue sites, including bone marrow, cardiovascular, hematopoietic, liver, lung, mammary gland, prostate, and other tissues [41]. For example, Sca-1 has been found on skeletal muscle progenitor cells, where it is associated with insulin-degrading enzyme [42]. Since insulin-degrading enzyme catabolizes mitogenic peptides, this may underlie the signaling pathway mediating Sca-1 actions [42].…”

“…For example, Sca-1 has been found on skeletal muscle progenitor cells, where it is associated with insulin-degrading enzyme [42]. Since insulin-degrading enzyme catabolizes mitogenic peptides, this may underlie the signaling pathway mediating Sca-1 actions [42]. Likewise, the function of Sca-1 has been evaluated extensively in lymphoid cell models where downstream kinase mechanisms have been implicated but not proven [41].…”

Delayed enrichment of mesenchymal cells promotes cardiac lineage and calcium transient development

“…Since it has been demonstrated that Sca-1 + cells possess stem-progenitor properties [17, 18] and that CD117 + cells have the potential to differentiate into a cardiac lineage [12], we used FACS analysis to evaluate the amount of CD117/Sca-1 initially present on EP, IP, and LP. The results indicated that approximately 10% of EP cells were positive for CD117/Sca-1, whereas IPs exhibited approximately 1% of CD117/Sca-1 + , and LPs only 0.01% of CD117/Sca-1 + cells, Figure S2 A, B, and C show the FACS results of EP, IP, and LP respectively.…”

High-Throughput Tracking of Pluripotent Human Embryonic Stem Cells with Dual Fluorescence Resonance Energy Transfer Molecular Beacons

“…hESCs sorted on the basis of FRET were plated on cover slips, fixed with 4% paraformaldehyde, and then stained for Oct4 expression and counterstained with DAPI as previously described [16]. hEBs were plated on cover slips for differentiation, fixed with 4% paraformaldehyde at 21 days after transfer to differentiation medium, and then permeabilized, fixed, and stained for β-III-tubulin, smooth muscle actin, and α-fetoprotein expression as previously described [12].…”