Abstract: TH-PO898
Activated Alpha 2-Macroglobulin (α2M*) Mediates High Glucose-Induced Cell Surface GRP78 Activation and Profibrotic Responses in Mesangial Cells
Session Information
- Diabetic Kidney Disease: Basic - I
November 07, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Diabetic Kidney Disease
- 601 Diabetic Kidney Disease: Basic
Authors
- Trink, Jackie, McMaster University, Hamilton, Ontario, Canada
- Li, Renzhong, McMaster University, Hamilton, Ontario, Canada
- Biltoft, Daniel, University of Southern Denmark, Esbjerg, Denmark
- Palarasah, Yaseelan, University of Southern Denmark, Esbjerg, Denmark
- Van krieken, Richard, McMaster University, Hamilton, Ontario, Canada
- Gao, Bo, St. Joseph's Hospital, Hamilton, Ontario, Canada
- Krepinsky, Joan C., McMaster University, St. Joseph's Hospital, Hamilton, Ontario, Canada
Background
Diabetic nephropathy is the leading cause of kidney failure in developed countries, characterized by glomerular accumulation of extracellular matrix proteins. High glucose (HG) induction of glomerular mesangial cell (MC) profibrotic responses plays a central role in its pathogenesis. We recently showed that the endoplasmic reticulum resident protein GRP78 translocates to the cell surface in response to HG to mediate Akt activation and profibrotic responses in MC. We also identified mesangial cell surface GRP78 (csGRP78) in vivo in diabetic mice. How csGRP78 is activated by HG, however, is unknown. The general protease inhibitor α2M, upon binding and activation by a protease, is known to interact with csGRP78 in cancer cells to elicit prosurvival signaling. Importantly, α2M was shown to be increased in diabetic patients’ serum and saliva. We thus investigated its role in HG profibrotic responses in MC.
Methods
Primary rat and mouse MC were treated with HG (30mM) or the osmotic control mannitol and responses assessed using standard molecular biology techniques. Kidneys from type 1 diabetic Akita mice were stained for α2M and the activated α2M*.
Results
HG, but not mannitol, increased α2M mRNA and protein expression as well as media secretion by 24h. Significantly more α2M* was also seen in media after HG treatment. By immunohistochemistry, both native α2M and activated α2M* were increased in glomeruli and tubules of type 1 diabetic Akita kidneys, with expression increasing to 40 weeks of age. By immunofluorescence, glomerular α2M* was localized to the mesangium, identified by α8 integrin positivity. Knockdown of α2M prevented HG-induced Akt activation and upregulation of the matrix proteins collagen IV and fibronectin. Neutralization of α2M* using an antibody specific for the activated form prevented HG-induced matrix protein upregulation.
Conclusion
Production and activation of α2M is increased by HG in MC and in diabetic kidneys, and mediates HG-induced matrix upregulation. Future studies will determine whether inhibiting α2M* interaction with csGRP78 is an effective therapeutic target for the treatment of diabetic nephropathy.
Funding
- Other NIH Support