Soluble Heparin Binding Epidermal Growth Factor-Like Growth Factor Is a Regulator ofGALGT2Expression andGALGT2-Dependent Muscle and Neuromuscular Phenotypes

Abstract

ABSTRACTGALGT2(alsoB4GALNT2) encodes a glycosyltransferase that is normally confined to the neuromuscular and myotendinous junction in adult skeletal muscle.GALGT2overexpression in muscle can inhibit muscular dystrophy in mouse models of the disease by inducing the overexpression of surrogate muscle proteins, including utrophin, agrin, laminins, and integrins. Despite its well-documented biological properties, little is known about the endogenous regulation of muscleGALGT2expression. Here, we demonstrate that epidermal growth factor receptor (EGFR) ligands can activate the humanGALGT2promoter. Overexpression of one such ligand, soluble heparin-binding EGF-like growth factor (sHB-EGF), also stimulated mouse muscleGalgt2gene expression and expression ofGALGT2-inducible surrogate muscle genes. Deletion analysis of theGALGT2promoter identified a 45-bp region containing a TFAP4-binding site that was required for sHB-EGF activation. sHB-EGF increased TFAP4 binding to this site in muscle cells and increased endogenousTfap4gene expression. sHB-EGF also increased muscle EGFR protein expression and activated EGFR-Akt signaling. sHB-EGF expression was concentrated at the neuromuscular junction, andHbegfdeletion reducedGalgt2-dependent synaptic glycosylation.Hbegfdeletion also mimickedGalgt2-dependent neuromuscular and muscular dystrophy phenotypes. These data demonstrate that sHB-EGF is an endogenous regulator of muscleGalgt2gene expression and can mimicGalgt2-dependent muscle phenotypes.