title: Regulation of CD2-associated protein influences podocyte endoplasmic reticulum stress-mediated apoptosis induced by albumin overload.
abstract: Proteinuria is an exacerbating factor of chronic kidney diseases, leading to glomerulosclerosis. However, the molecular mechanisms mediating protein overload-induced podocyte injury are poorly understood. Recent studies have shown that apoptosis mediated by endoplasmic reticulum (ER) stress participated in the progression of a variety of kidney diseases. In the present study, we investigated the role of CD2-associated protein (CD2AP) in protein overload-induced ER stress and subsequent podocyte apoptosis. Conditionally immortalized mouse podocytes were cultured in vitro and treated with different concentrations of bovine serum albumin (BSA). In addition, CD2AP eukaryotic expression vector or siRNA was transfected into podocytes before exposed to BSA. Albumin endocytosis and podocyte apoptosis were visualized by confocal microscopy. The subcellular organelles were observed by transmission electron microscopy. The expressions of GRP78, caspase-12 and CD2AP were detected by RT-PCR or Western blot analysis. It was found that albumin was endocytosed by podocytes in a time-dependent manner. Accumulation of albumin in podocytes induced ER stress and apoptosis in a concentration-dependent manner as indicated by upregulation of GRP78 and caspase-12. Meanwhile, the subcellular organelles were disrupted and the expression of CD2AP was downregulated by high concentration of albumin. Transfection of CD2AP eukaryotic expression vector into podocytes increased CD2AP expression, depressed GRP78 and caspase-12 expressions, and inhibited podocyte apoptosis. In contrast, transfection of CD2AP siRNA deteriorated the above changes induced by BSA. It is concluded protein overload induces podocyte apoptosis via ER stress and CD2AP may play a crucial role in albumin overload-induced ER stress and apoptosis in podocytes.
authors.affiliation: Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
authors.forename: Fangfang
authors.initials: F
authors.lastname: He
authors.forename: Shan
authors.initials: S
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Ning
authors.initials: N
authors.lastname: Shao
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Tian
authors.forename: Huajun
authors.initials: H
authors.lastname: Jiang
authors.forename: Jianshe
authors.initials: J
authors.lastname: Liu
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Zhu
authors.forename: Xianfang
authors.initials: X
authors.lastname: Meng
authors.forename: Chun
authors.initials: C
authors.lastname: Zhang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002461:Cell Line, Transformed; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004705:Endocytosis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D051379:Mice; D050199:Podocytes / Q000378:metabolism*; D011507:Proteinuria / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000494:pharmacology*; D013312:Stress, Physiological; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C114545:CD2-associated protein; D003598:Cytoskeletal Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717248:Hspa5 protein, mouse; D012710:Serum Albumin, Bovine