Background : Transplant glomerulopathy(TG) a histological manifestation of chronic antibody mediated rejection and a major cause of late allograft loss. It is well accepted that donor specific antibodies (DSA) represent a risk factor for development of TG . TG is thought to develop following endothelial injury yet increase in urine Podocin/Creatinine ratio in TG signifies marked acceleration of podocyte detachment from glomerular basement membrane. Calcium calmodulin kinase IV (CAMK4) is a serine threonine kinase that has been shown to be up-regulated in podocytes of patients with lupus nephritis through a mechanism involving the presence or autoantibodies. Here we evaluated the expression of CaMKIV in kidney biopsy specimens from patients with TG and in a human podocyte cell line (AB8/13) after exposure to IgG from sera of patients with TG.

Methods: We examined the expression of CaMKIV in TG kidney specimens along with kidney biopsies from patients without TG but with other forms of allograft dysfunction including thrombotic microangiopathy and BK virus nephropathy, by immunofluorescence staining. We also cultured human podocytes with IgG purified from sera of patients with and without TG for 24 hrs and determined CaMKIV expression levels by Western blotting. Furthermore, we evaluated evidence of podocyte and slit diaphragm integrity by measuring nephrin mRNA by RT-PCR, synaptopodin and alpha actinin-4 expression by western blot, after exposure of the podocyte cell line to IgG from patients with TG.

Results: CaMKIV expression was found increased in podocytes of TG kidney biopsy specimens but not in samples without TG. Interestingly, culture of AB8/13 podocytes in the presence of TG sera led to an increase in CAMKIV expression in a dose dependent manner. After exposure of these cells to IgG depleted sera and purified IgG from TG patients, CAMKIV expression was noted to increase after exposure to the IgG but not to the non-IgG fraction. Increase in CAMK4 expression resulted in decreased nephrin and alpha actinin-4 expression.

Conclusion: Our data demonstrate increased expression of CaMKIV in podocytes from TG patients and that IgG from sera of these patients caused increased CaMKIV in cultured podocytes. Increased CaMKIV expression may contribute to the inability of podocytes to maintain the integrity of glomerular basement membrane in TG and this may represent a novel biomarker for the detection of TG and a pathway for development of novel therapeutics.

CITATION INFORMATION: Bhargava R., Maeda K., Ferreti A., Pavlakis M., Tsokos G. Role of Calcium/Calmodulin Kinase IV on Podocyte Function in Transplant Glomerulopathy Am J Transplant. 2017;17 (suppl 3).

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