Post-Translational Regulation of CD133 by ATase1/ATase2-Mediated Lysine Acetylation

Abstract

The CD133 cell surface protein expresses the AC133 epitope that is associated with cancer progenitor cells and resistance to traditional anticancer therapies. We report that the endoplasmic reticulum Golgi intermediate compartment residing acetyltransferases, ATase1 and ATase2, can physically interact with CD133 to acetylate the protein on three lysine residues predicted to reside on the first extracellular loop of CD133. Site-directed mutagenesis of these residues mimicking a loss of acetylation and downregulation or inhibition of ATase1/ATase2, resulted in near complete abolishment of CD133 protein expression. We also demonstrate that targeting ATase1/ATase2 results in apoptosis of CD133 expressing acute lymphoblastic leukemia cells. Taken together, we suggest that lysine acetylation on predicted extracellular residues plays a key role in expression and trafficking of CD133 protein to the cell surface and can be targeted to disrupt CD133 regulation and function.

The Endoplasmic Reticulum-based Acetyltransferases, ATase1 and ATase2, Associate with the Oligosaccharyltransferase to Acetylate Correctly Folded Polypeptides

“…Indeed, acetylated intermediates of BACE1 could move through the secretory pathway, whereas nonacetylated intermediates could not (2). Similar conclusions were recently reached with CD133 (13). Therefore, in light of the above findings, we can interpret the association of the ATases with the OST complex as follows: the OST initially recognizes the NX(T/S) consensus motif on nascent glycoproteins and proceeds to transfer the GlcNAc 2 Man 9 Glc 3 oligosaccharide to the Asn residue (Fig.…”

“…Since then, many proteins that undergo the same process have been identified, either through proteomics or direct analysis (4,13,29). Here, we report that the ER-based acetyltransferases, ATase1 and ATase2, assemble to form homo-and heterodimers and associate with four (perhaps five) members of the OST complex.…”

“…Incorrectly folded glycoproteins will not be recognized by the ATases (Fig. 8B) and therefore will not be allowed to proceed through the secretory pathway (2,13). Interestingly enough, as with the UDPglucose:glycoprotein glucosyltransferase/calnexin system, N ⑀ -lysine acetylation is also a transient event.…”

“…An example is the role that the mitochondria acetylation machinery plays in cell metabolism (12). So far, the role of lysine acetylation in the lumen of the ER has only been dissected for two type I membrane proteins, BACE1 and CD133 (2,13). BACE1 is involved in the pathogenesis of Alzheimer disease (14,15), whereas CD133 appears to regulate the "stemness potential" of cancer cells (16 -18).…”

“…Both are active targets for therapeutics. Although there are subtle differences, in both cases deficient acetylation of the nascent protein resulted in deficient trafficking, retention in the early secretory pathway, and rapid degradation (2,13).…”