The endoplasmic reticulum chaperone ERdj4 is required for survival, glucose metabolism and B cell development

The ER-localized DnaJ homologue 4 (ERdj4) is a soluble ER chaperone induced by the unfolded protein response (UPR) to assist in the removal of unfolded/misfolded proteins from the ER lumen for proteasomal degradation. To elucidate the function of ERdj4 in vivo, ERdj4 gene trap mice were generated from embryonic stem cells harboring a gene trap cassette inserted into the ERdj4 locus. ERdj4 gene trap mice expressed hypomorphic levels of ERdj4 with a 10-100 fold reduction in all tissues and cell types examined. Approximately 30-50% of ERdj4 gene trap mice died perinatally in association with growth retardation and hypoglycemia. ERdj4 gene trap neonates exhibited signs of delayed pancreatic development, including abnormal distribution of pancreatic α- and β-cells and reduced insulin and glucagon in the pancreas. Surviving adult ERdj4 gene trap mice were glucose intolerant, resulting from hypoinsulinemia rather than insulin resistance. Pancreatic β-cells exhibited increased ER stress, including ER dilation and upregulation of the UPR. Proinsulin accumulated in the ER of β-cells from ERdj4 gene trap mice consistent with our previous finding that proinsulin is a substrate for ERdj4. The insulin processing enzymes, including Pcsk1, Pcsk2 and CPE, also associated with ERdj4, contributing to defects in proinsulin biosynthesis in ERdj4 gene trap mice. ERdj4 deficiency also resulted in pancreatic a-cell hyperplasia in association with increased ER stress. Since previous studies had demonstrated that the UPR is required for both early and late B lymphopoiesis, we hypothesized that ERdj4 deficiency would affect B cell development. Pro-B, pre-B, immature and mature B cell populations were significantly reduced in the bone marrow of ERdj4 gene trap mice in association with increased pro-B cell death. Further, mature B cell populations were reduced in the spleen and peritoneal cavity. ERdj4 gene trap donor cells transplanted into wildtype recipients rescued all stages of B cell development, confirming a defect in the microenvironment. Osteogenic cells support B cell development and the UPR is required for osteoblast differentiation and function. Bone-lining cells, which differentiate from osteoblasts, were reduced in ERdj4 gene trap mice in association with increased ER stress. Further, primary bone cells from ERdj4 gene trap mice had reduced expression of osteogenic-specific markers. These data suggest that the loss of ERdj4 affects the maturation/survival of osteogenic cells, which in turn leads to a defect in B lymphopoiesis. Collectively, this work reveals an important role for ERdj4 in survival, glucose metabolism and B cell development.

Name thesis:degree_name

PhD

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Medicine: Immunology

Grantor dc:publisher

University of Cincinnati

Year dc:date

2012

Author dc:creator

• Fritz, Jill M.

Contributors dc:contributor

• Weaver, Timothy

• Molecular Biology
• ERdj4
• UPR
• molecular chaperones
• endoplasmic reticulum
• glucose metabolism
• B cell development

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353950480

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ucin1353950480