title: Assessing the contribution of thrombospondin-4 induction and ATF6α activation to endoplasmic reticulum expansion and phenotypic modulation in bladder outlet obstruction.
abstract: Phenotypic modulation of smooth muscle cells is a hallmark of disease. The associated expansion of endoplasmic reticulum (ER) volume remains unexplained. Thrombospondin-4 was recently found to promote ATF6α activation leading to ER expansion. Using bladder outlet obstruction as a paradigm for phenotypic modulation, we tested if thrombospondin-4 is induced in association with ATF6α activation and ER expansion. Thrombospondin-4 was induced and ATF6α was activated after outlet obstruction in rodents. Increased abundance of spliced of Xbp1, another ER-stress sensor, and induction of Atf4 and Creb3l2 was also seen. Downstream of ATF6α, Calr, Manf, Sdf2l1 and Pdi increased as did ER size, whereas contractile markers were reduced. Overexpression of ATF6α, but not of thrombospondin-4, increased Calr, Manf, Sdf2l1 and Pdi and caused ER expansion, but the contractile markers were inert. Knockout of thrombospondin-4 neither affected bladder growth nor expression of ATF6α target genes, and repression of contractile markers was the same, even if ATF6α activation was curtailed. Increases of Xbp1s, Atf4 and Creb3l2 were similar. Our findings demonstrate reciprocal regulation of the unfolded protein response, including ATF6α activation and ER expansion, and reduced contractile differentiation in bladder outlet obstruction occurring independently of thrombospondin-4, which however is a sensitive indicator of obstruction.
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Katarzyna K
authors: KK
authors: Krawczyk
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Mari
authors: M
authors: Ekman
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Catarina
authors: C
authors: Rippe
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Mario
authors: M
authors: Grossi
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Bengt-Olof
authors: BO
authors: Nilsson
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Sebastian
authors: S
authors: Albinsson
authors: Department of Urology, Clinical Sciences, Lund University, Lund, Sweden.
authors: Bengt
authors: B
authors: Uvelius
authors: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors: Karl
authors: K
authors: Swärd
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism; D051702:Activating Transcription Factor 6 / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D064032:Calbindin 2 / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D059865:Endoplasmic Reticulum Stress / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D019699:Thrombospondins / Q000172:deficiency / Q000235:genetics*; D056811:Unfolded Protein Response; D014521:Urethra / Q000601:surgery; D001748:Urinary Bladder Neck Obstruction / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000071717:X-Box Binding Protein 1 / Q000235:genetics / Q000378:metabolism
chemical_list: D051702:Activating Transcription Factor 6; C497110:Atf4 protein, rat; C497112:Atf6 protein, mouse; D050976:Basic-Leucine Zipper Transcription Factors; C576512:Calb2 protein, rat; D064032:Calbindin 2; C544811:Creb3l2 protein, mouse; C546826:MANF protein, rat; D008565:Membrane Proteins; D009414:Nerve Growth Factors; D019699:Thrombospondins; D000071717:X-Box Binding Protein 1; C000605545:Xbp1 protein, rat; C486021:sdf2l1 protein, mouse; C101864:thrombospondin 4; D051701:Activating Transcription Factor 4