The unfolded protein response is activated in connexin 50 mutant mouse lenses.
The unfolded protein response is a set of cell signaling pathways recently recognized to be activated in the lens during both normal development and endoplasmic reticulum stress induced by either unfolded proteins or oxidative damage. While mutations in the gene for connexin 50 are known to cause autosomal dominant cataracts, it has not been previously reported whether mutant connexins can activate the unfolded protein response in the lens. Mice homozygous for the S50P or G22R mutation of connexin 50 have reduced amounts of connexin 50 protein at the cell membrane, with some intracellular staining consistent with retention in the endoplasmic reticulum. Connexin 50 mutants have elevated levels of BiP expression in both lens epithelial and fiber cells from E15.5 with the most robust elevation detected in newborns. While this elevation decreases in magnitude postnatally, BiP expression is still abnormally high in adults, particularly in the perinuclear endoplasmic reticulum of cell nuclei that are inappropriately retained in adult homozygous mutant lenses. Xbp1 splicing was elevated in lenses from both connexin mutants studied, while Atf4 and Atf6 levels were not majorly affected. Overall, these data suggest that UPR may be a contributing factor to the phenotype of connexin 50 mutant lenses even though the relatively modest extent of the response suggests that it is unlikely to be a major driver of the pathology.
Department of Biological Sciences, University of Delaware, 327 Wolf Hall, The Green, Newark, DE 19716, USA.
Bhagwat V
BV
Alapure
Jaime K
JK
Stull
Zeynep
Z
Firtina
Melinda K
MK
Duncan
D051701:Activating Transcription Factor 4 / Q000235:genetics; D051702:Activating Transcription Factor 6 / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002386:Cataract / Q000378:metabolism*; D017630:Connexins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D000091342:Endoplasmic Reticulum Chaperone BiP; D005136:Eye Proteins / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000378:metabolism; D007908:Lens, Crystalline / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000235:genetics; D056811:Unfolded Protein Response / Q000502:physiology*; D000071717:X-Box Binding Protein 1; D000099264:Connexin 50
D051701:Activating Transcription Factor 4; D051702:Activating Transcription Factor 6; D017630:Connexins; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D005136:Eye Proteins; D006360:Heat-Shock Proteins; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; D000099264:Connexin 50; C081452:Atf4 protein, mouse; C497112:Atf6 protein, mouse; C000605544:Xbp1 protein, mouse