Neuronatin is a stress-responsive protein of rod photoreceptors.
Neuronatin (NNAT) is a small transmembrane proteolipid that is highly expressed in the embryonic developing brain and several other peripheral tissues. This study is the first to provide evidence that NNAT is detected in the adult retina of various adult rod-dominant mammals, including wild-type (WT) rodents, transgenic rodents expressing mutant S334ter, P23H, or T17M rhodopsin, non-human primates, humans, and cone-dominant tree shrews. Immunohistochemical and quantitative real time polymerase chain reaction (qRT-PCR) analyses were applied to detect NNAT. Confocal microscopy analysis revealed that NNAT immunofluorescence is restricted to the outer segments (OSs) of photoreceptors without evidence of staining in other retinal cell types across all mammalian species. Moreover, in tree shrew retinas, we found NNAT to be co-localized with rhodopsin, indicating its predominant expression in rods. The rod-derived expression of NNAT was further confirmed by qRT-PCR in isolated rod photoreceptor cells. We also used these cells to mimic cellular stress in transgenic retinas by treating them with the endoplasmic reticulum stress inducer, tunicamycin. Thus, our data revealed accumulation of NNAT around the nucleus as compared to dispersed localization of NNAT within control cells. This distribution coincided with the partial intracellular mislocalization of NNAT to the outer nuclear layer observed in transgenic retinas. In addition, stressed retinas demonstrated an increase of NNAT mRNA and protein levels. Therefore, our study demonstrated that NNAT is a novel stress-responsive protein with a potential structural and/or functional role in adult mammalian retinas.
University of Alabama at Birmingham, Department of Optometry, United States; University of Alabama at Birmingham, Department of Vision Science, School of Optometry, United States.
Vishal
V
Shinde
University of Alabama at Birmingham, Department of Optometry, United States; University of Alabama at Birmingham, Department of Vision Science, School of Optometry, United States.
Priyamvada M
PM
Pitale
University of Alabama at Birmingham, Department of Optometry, United States; University of Alabama at Birmingham, Department of Vision Science, School of Optometry, United States.
Wayne
W
Howse
University of Alabama at Birmingham, Department of Optometry, United States; University of Alabama at Birmingham, Department of Vision Science, School of Optometry, United States.
Oleg
O
Gorbatyuk
University of Alabama at Birmingham, Department of Optometry, United States; University of Alabama at Birmingham, Department of Vision Science, School of Optometry, United States. Electronic address: mgortk@uab.edu.
Marina
M
Gorbatyuk
D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D059865:Endoplasmic Reticulum Stress / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D012162:Retinal Degeneration / Q000378:metabolism / Q000473:pathology; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism* / Q000473:pathology; D012174:Retinitis Pigmentosa / Q000378:metabolism / Q000473:pathology; D013045:Species Specificity; D013312:Stress, Physiological / Q000502:physiology*; D014415:Tunicamycin; D014418:Tupaiidae
D008565:Membrane Proteins; C490237:NNAT protein, human; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D014415:Tunicamycin
ER stress; autosomal dominant retinitis pigmentosa; neuronatin; retinal degeneration; rod photoreceptors