Characterization of the kidney pathology in Mucolipidosis type IV (MLIV)
Awardee: Diego Luis Medina
Institution: Telethon Institute of Genetics and Medicine (TIGEM)
Grant Amount: $53,634.00
Funding Period: February 1, 2023 - January 31, 2024
Summary:
TRPML1 (Transient Receptor Potential cation channel, Mucolipin subfamily1) is a non-selective cation channel that localize on lysosomal membrane. The protein TRPML1 is encoded by MCOLN1 (mucolipin1) gene. TRPML1 is the major calcium-release channel on the lysosomal membrane. TRPML1 activity is involved in a variety of membrane trafficking processes such as lysosome to TGN (Trans-Golgi-Network) retrograde trafficking, AV-lysosome fusion, lysosome reformation, and lysosomal exocytosis. Mutations in TRPML1 cause mucolipidosis type IV (MLIV: OMIM 252650), an autosomal recessive LSD (lysosomal Storage Disease) characterized by psychomotor alteration, corneal opacities, and achlorhydria, but its role in kidney it’s not completely understood. Recently acute or chronic renal diseases been observed in a subset of patients affected by MLIV. The host laboratory has an extensive expertise in the study of the cell biology processes controlling lysosomal signaling through TRPML1. Recently, Medina’s laboratory has observed that pharmacological activation of TRPML1 can induce autophagosome biogenesis through the generation of PI3P (phosphatidylinositol 3-phosphate) via Vps34 complex (Vacuolar Protein Sorting 34), thus suggesting that alterations in Vps34 pathway might be part of the pathologic features of MLIV. interestingly, this novel pathway is impaired in human fibroblasts from MLIV patients (Scotto-Rosato et al, 2020). Autophagosome is a cellular organelle characterize by characterized by a double layer membranes. It is the key structure in macro autophagy, the intracellular degradation system for cytoplasmic contents. In this proposal our principal goal is to investigate the physiological relevance of TRPML1 in kidney using an in vivo mouse model of MLIV (mouse model available in the animal facility of our institute). Thus, in addition to general parameters such as weight and size of kidney organs, we will analyze the general morphology of nephron by using specific markers of kidney cells. Also, we will investigate kidney functionality defects including (i) inflammation and (ii) proteinuria. Its’ know that prevalence of inflammation is inversely related to the level of kidney function and positively associated with the magnitude of proteinuria. There are many factors that contributes to the inflammation status as well as increased production of proinflammatory cytokines, we will study the principal biomarkers of inflammation. The second goal will be studied by using state-of-the-art proteomics from urine samples of MLIV mice. The proteomic procedure determines the pathophysiological meaning and clinical relevance of results in the field of nephrology. The benefits of employing urinary proteomics for biomarker discovery are that urine is readily available, easy to collect and provides a renewable and non-invasive means of monitoring a patient over time. At the cellular level, we will determine the consequences of TRPML1 depletion on (i) the endocytic pathways and (ii) autophagy. Interestingly, our preliminary data in kidneys show that MLIV mice exhibit a low molecular weigh (LMW) that suggest a defective apical recycling mediate endocytosis (ARME) in Proximal Tubule (PT), section of nephron that captures all protein that pass through the glomerulus), lysosomal mislocalization and swelling of structures labelled by LAMP-1, these data suggest a block of autophagy. Furthermore, the MLIV kidneys show a TFEB nuclear translocation, an increased signal of galectin-3 and F4/80 (major macrophage marker). Understanding the mechanism of kidney damage and renal failure in MLIV is of critical importance. It is known that inhibition of calcineurin the kidneys by CSA can lead to acute and chronic injury. We will focus on the axis: TRMPL1-TFEB-Calcineurin signaling. Since renal disease in both human and model are poorly defined, we contacted and established a scientific collaboration Dr. Albert Misko, which is running the biggest natural history study in MLIV patients, and Prof. Yulia Griskuck a world-recognized expert in the study of MLIV disease (both from the MGH, US). This collaboration will allow to share mouse samples and compare the emerging mouse renal pathology with the natural history data from patients. The knowledge from these studies might be of interest for further studies to characterize and develop novel therapeutics to treat this devastating disease.