Vps34/PI3KC3 deletion in kidney proximal tubules impairs apical trafficking and blocks autophagic flux, causing a Fanconi-like syndrome and renal insufficiency

Abstract

Kidney proximal tubular cells (PTCs) are highly specialized for ultrafiltrate reabsorption and serve as paradigm of apical epithelial differentiation. Vps34/PI3-kinase type III (PI3KC3) regulates endosomal dynamics, macroautophagy and lysosomal function. However, its in vivo role in PTCs has not been evaluated. Conditional deletion of Vps34/PI3KC3 in PTCs by Pax8-Cre resulted in early (P7) PTC dysfunction, manifested by Fanconi-like syndrome, followed by kidney failure (P14) and death. By confocal microscopy, Vps34 PTCs showed preserved apico-basal specification (brush border, NHERF-1 versus Na/K-ATPase, ankyrin-G) but basal redistribution of late-endosomes/lysosomes (LAMP-1) and mis-localization to lysosomes of apical recycling endocytic receptors (megalin, cubilin) and apical non-recycling solute carriers (NaPi-IIa, SGLT-2). Defective endocytosis was confirmed by Texas-red-ovalbumin tracing and reduced albumin content. Disruption of Rab-11 and perinuclear galectin-3 compartments suggested mechanistic clues for defective receptor recycling and apical biosynthetic trafficking. p62-dependent autophagy was triggered yet abortive (p62 co-localization with LC3 but not LAMP-1) and PTCs became vacuolated. Impaired lysosomal positioning and blocked autophagy are known causes of cell stress. Thus, early trafficking defects show that Vps34 is a key in vivo component of molecular machineries governing apical vesicular trafficking, thus absorptive function in PTCs. Functional defects underline the essential role of Vps34 for PTC homeostasis and kidney survival.

Electropreconcentration diagrams to optimize molecular enrichment with low counter pressure in a nanofluidic device

“…Chicken ovalbumin is a 45 kDa protein that is the major component of egg white. Fluorescent ovalbumin can be used as endocytic tracers [33‐35] and to estimate the size of the transport pathways of micro‐vessels [36]. It is also used in various research fields such as studying the structure and functionality of serpins, and proteomics (egg yolk ovalbumin is frequently used as a molecular marker for calibration of electrophoresis gels) or immunology frequently used to stimulate an allergic reaction on test subjects [37,38].…”

Multiple phosphatidylinositol(3)phosphate roles in retinal pigment epithelium membrane recycling

“…Vps34 function is required for completion of autophagy, and knockout of Vps34 has been shown to result in arrest prior to autophagolysosome formation in every cell type tested (Zhou et al, 2010;Jaber et al, 2012;Bechtel et al, 2013;He et al, 2016He et al, , 2019Grieco et al, 2018). Similarly, in the KO RPE, puncta containing LC3 and autophagy proteins Atg9 and p62 accumulated ( Fig 4A,E,F,5A,E) and colocalized ( Fig 5C,D), along with ubiquitinated proteins ( Fig 5G).…”

The tripartite interaction of phosphate, autophagy, and αKlotho in health maintenance

“…The decreased plasma Pi and increased urinary Pi excretion in mice after adminstration of TB-11, the active and functional peptide of beclin 1 futher proves the concept that high autophagy in the kidney promotes negative Pi balance. The restored body growth and reduced mortality in BK/BK;kl/kl mice was abolished by high-Pi diet further The role of autophagy in regulation of renal transport 66,67 including water, 68,69 glucose, 70 cysteine, 71 and other electrolytes 72 have been reported. The current manuscript provides new data linking autophagy with phosphate transport in the renal tubules.…”

“…The role of autophagy in regulation of renal transport including water, glucose, cysteine, and other electrolytes have been reported. The current manuscript provides new data linking autophagy with phosphate transport in the renal tubules.…”