O-linked β-N-acetylglucosamine modification of proteins is essential for foot process maturation and survival in podocytes.
BACKGROUND
O-linked β- N -acetylglucosamine modification O-GlcNAcylation) is a post-translational modification of intracellular proteins, serving as a nutrient sensor. Growing evidence has demonstrated its physiological and pathological importance in various mammalian tissues. This study examined the physiological role of O-GlcNAcylation in podocyte function and development.


METHODS
O-GlcNAc transferase (Ogt) is a critical enzyme for O-GlcNAcylation and resides on the X chromosome. To abrogate O-GlcNAcylation in podocytes, we generated congenital and tamoxifen (TM)-inducible podocyte-specific Ogt knockout mice (Podo-Ogt y/- and TM-Podo-Ogt y/- , respectively) and analyzed their renal phenotypes.


RESULTS
Podo-Ogt y/- mice showed normal podocyte morphology at birth. However, they developed albuminuria at 8 weeks of age, increasing progressively until age 32 weeks. Glomerular sclerosis, proteinuria-related tubulointerstitial lesions and markedly altered podocyte foot processes, with decreased podocin expression, were observed histologically in 32-week-old Podo-Ogt y/- mice. Next, we induced adult-onset deletion of the Ogt gene in podocytes by TM injection in 8-week-old TM-Podo-Ogt y/- mice. In contrast to Podo-Ogt y/- mice, the induced TM-Podo-Ogt y/- mice did not develop albuminuria or podocyte damage, suggesting a need for O-GlcNAcylation to form mature foot processes after birth. To test this possibility, 3-week-old Podo-Ogt y/- mice were treated with Bis-T-23, which stimulates actin-dependent dynamin oligomerization, actin polymerization and subsequent foot process elongation in podocytes. Albuminuria and podocyte damage in 16-week-old Podo-Ogt y/- mice were prevented by Bis-T-23 treatment.


CONCLUSIONS
O-GlcNAcylation is necessary for maturation of podocyte foot processes, particularly after birth. Our study provided new insights into podocyte biology and O-GlcNAcylation.
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Shinya
S
Ono
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Shinji
S
Kume
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Mako
M
Yasuda-Yamahara
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Kosuke
K
Yamahara
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Naoko
N
Takeda
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Masami
M
Chin-Kanasaki
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Hisazumi
H
Araki
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Osamu
O
Sekine
Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Hideki
H
Yokoi
Department of Nephrology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
Masashi
M
Mukoyama
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Takashi
T
Uzu
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Shin-Ichi
SI
Araki
Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
Hiroshi
H
Maegawa
D000117:Acetylglucosamine / Q000737:chemistry*; D000818:Animals; D005260:Female; D005528:Foot / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017351:N-Acetylglucosaminyltransferases / Q000502:physiology*; D050199:Podocytes / Q000378:metabolism*; D011499:Protein Processing, Post-Translational
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C407223:NPHS2 protein; D017351:N-Acetylglucosaminyltransferases; C449880:O-GlcNAc transferase; D000117:Acetylglucosamine
O-GlcNAcylation; O-linked N-acetylglucosamine transferase; foot process; podocyte