Embryonic growth-associated protein is one subunit of a novel N-terminal acetyltransferase complex essential for embryonic vascular development.
N-terminal protein acetylation, catalyzed by N-terminal acetyltransferases (NATs) recognizing distinct N-terminal sequences, is gaining recognition as an essential regulator of normal cell function, but little is known of its role in vertebrate development. We previously cloned a novel gene, embryonic growth-associated protein (EGAP), the expression of which is associated with rapid vascular smooth muscle cell proliferation during development. We show herein EGAP is the mammalian/zebrafish homologue of yeast Mak10p, one subunit of the yeast NatC complex, and describe the cloning of its binding partners Mak3 and Mak31. The EGAP NAT forms a functional complex in mammalian cells, is evolutionarily conserved, and developmentally regulated. It is widely but not ubiquitously expressed during early zebrafish development but undetectable in later developmental stages. We demonstrate EGAP- and Mak3-deficient zebrafish fail to develop because of, in part, decreased cell proliferation, increased apoptosis, and poor blood vessel formation contributing to embryonic lethality. We examined the role of target of rapamycin (TOR), a highly conserved protein kinase controlling cell growth, as a physiological target of EGAP NAT acetylation. Compared with controls, TOR expression and signaling is significantly reduced in EGAP morphants. Pharmacological inhibition of TOR with rapamycin phenocopied the EGAP morpholino oligonucleotide-induced growth and vessel defects. Overexpression of constitutively active TOR rescued EGAP morphants, suggesting TOR is a direct or indirect endogenous substrate of the EGAP NAT complex. These data suggest the EGAP NAT complex is an essential regulatory enzyme controlling the function of a subset of proteins required for embryonic growth control and vessel development.
Department of Renal Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Janet M
JM
Wenzlau
Pamela J
PJ
Garl
Peter
P
Simpson
Kurt R
KR
Stenmark
James
J
West
Kristin B
KB
Artinger
Raphael A
RA
Nemenoff
Mary C M
MC
Weiser-Evans
D000107:Acetylation; D000123:Acetyltransferases / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D049109:Cell Proliferation; D047108:Embryonic Development; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000196:embryology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology; D021122:Protein Subunits; D011506:Proteins / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases; D015027:Zebrafish / Q000196:embryology*
D021122:Protein Subunits; D011506:Proteins; D000123:Acetyltransferases; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases