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A Specific Tubular ApoA-I Distribution Is Associated to FSGS Recurrence after Kidney Transplantation. J Clin Med 2021; 10:jcm10102174. [PMID: 34069888 PMCID: PMC8157584 DOI: 10.3390/jcm10102174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 05/14/2021] [Indexed: 01/27/2023] Open
Abstract
A major complication of primary focal segmental glomerulosclerosis (FSGS) is its recurrence after kidney transplantation that happens in 30 to 40% of the patients. The diagnosis of these relapses is not always easy as the histological lesions are not highly specific and appear after the proteinuria increase. Currently, there are no accurate biomarkers to detect FSGS recurrence. Our group identified a modified form of Apolipoprotein A-I (ApoA-I), named ApoA-Ib, specifically present in the urine of recurrent FSGS patients after kidney transplantation. Aberrant forms of ApoA-I have also been described in the urine of native primary FSGS patients; this feature has been associated with prominent staining of ApoA-I at the apical membrane of the tubular cells. In this study, we aim to analyze the ApoA-I distribution in kidney allograft biopsies of recurrent FSGS patients. We detected ApoA-I by immunohistochemistry in kidney allograft biopsies of patients with FSGS relapse after kidney transplantation and in kidney allograft biopsies of patients with a disease different from FSGS in the native kidney (non-FSGS). In recurrent FSGS patients, ApoA-I was prominently localized at the brush border of the tubular cells, while in the non-FSGS patients, ApoA-I was found along the cytoplasm of the tubular cells. The localization of ApoA-I at the brush border of the tubular cells is a specific feature of primary FSGS in relapse. This suggests that ApoA-I staining in kidney biopsies, coupled with ApoA-Ib measurement in urine, could be used as a diagnostic tool of primary FSGS relapse after kidney transplantation due to its highly specific tubular distribution.
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Jacobs-Cachá C, Puig-Gay N, Helm D, Rettel M, Sellarès J, Meseguer A, Savitski MM, Moreso FJ, Soler MJ, Seron D, Lopez-Hellin J. A misprocessed form of Apolipoprotein A-I is specifically associated with recurrent Focal Segmental Glomerulosclerosis. Sci Rep 2020; 10:1159. [PMID: 31980684 PMCID: PMC6981185 DOI: 10.1038/s41598-020-58197-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Accepted: 01/10/2020] [Indexed: 12/29/2022] Open
Abstract
Apolipoprotein A-Ib (ApoA-Ib) is a high molecular weight form of Apolipoprotein A-I (ApoA-I) found specifically in the urine of kidney-transplanted patients with recurrent idiopathic focal segmental glomerulosclerosis (FSGS). To determine the nature of the modification present in ApoA-Ib, we sequenced the whole APOA1 gene in ApoA-Ib positive and negative patients, and we also studied the protein primary structure using mass spectrometry. No genetic variations in the APOA1 gene were found in the ApoA-Ib positive patients that could explain the increase in its molecular mass. The mass spectrometry analysis revealed three extra amino acids at the N-Terminal end of ApoA-Ib that were not present in the standard plasmatic form of ApoA-I. These amino acids corresponded to half of the propeptide sequence of the immature form of ApoA-I (proApoA-I) indicating that ApoA-Ib is a misprocessed form of proApoA-I. The description of ApoA-Ib could be relevant not only because it can allow the automated analysis of this biomarker in the clinical practice but also because it has the potential to shed light into the molecular mechanisms that cause idiopathic FSGS, which is currently unknown.
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Affiliation(s)
- Conxita Jacobs-Cachá
- Nephrology Research Group, Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain. .,Nephrology Department, Hospital Vall d'Hebrón, Barcelona, Spain.
| | - Natàlia Puig-Gay
- Renal Physiopathology Group-CIBBIM. Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Dominic Helm
- Proteomics Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Mandy Rettel
- Proteomics Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Joana Sellarès
- Nephrology Research Group, Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain.,Nephrology Department, Hospital Vall d'Hebrón, Barcelona, Spain
| | - Anna Meseguer
- Renal Physiopathology Group-CIBBIM. Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Mikhail M Savitski
- Proteomics Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany.,Genome Biology, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Francesc J Moreso
- Nephrology Research Group, Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain.,Nephrology Department, Hospital Vall d'Hebrón, Barcelona, Spain
| | - Maria José Soler
- Nephrology Research Group, Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain.,Nephrology Department, Hospital Vall d'Hebrón, Barcelona, Spain
| | - Daniel Seron
- Nephrology Research Group, Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain.,Nephrology Department, Hospital Vall d'Hebrón, Barcelona, Spain
| | - Joan Lopez-Hellin
- Renal Physiopathology Group-CIBBIM. Hospital Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain. .,Biochemistry Department, Hospital Vall d'Hebrón, Barcelona, Spain.
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