Loss of PKD1/polycystin-1 impairs lysosomal activity in a CAPN (calpain)-dependent manner

Autophagy. 2021 Sep;17(9):2384-2400. doi: 10.1080/15548627.2020.1826716. Epub 2020 Oct 6.


Mutations in the PKD1 gene result in autosomal dominant polycystic kidney disease (ADPKD), the most common monogenetic cause of end-stage renal disease (ESRD) in humans. Previous reports suggested that PKD1, together with PKD2/polycystin-2, may function as a receptor-cation channel complex at cilia and on intracellular membranes and participate in various signaling pathways to regulate cell survival, proliferation and macroautophagy/autophagy. However, the exact molecular function of PKD1 and PKD2 has remained enigmatic. Here we used Pkd1-deficient mouse inner medullary collecting duct cells (mIMCD3) genetically deleted for Pkd1, and tubular epithelial cells isolated from nephrons of doxycycline-inducible conditional pkd1fl/fl;Pax8rtTA;TetOCre+ knockout mice to show that the lack of Pkd1 caused diminished lysosomal acidification, LAMP degradation and reduced CTSB/cathepsin B processing and activity. This led to an impairment of autophagosomal-lysosomal fusion, a lower delivery of ubiquitinated cargo from multivesicular bodies (MVB)/exosomes to lysosomes and an enhanced secretion of unprocessed CTSB into the extracellular space. The TFEB-dependent lysosomal biogenesis pathway was however unaffected. Pkd1-deficient cells exhibited increased activity of the calcium-dependent CAPN (calpain) proteases, probably due to a higher calcium influx. Consistent with this notion CAPN inhibitors restored lysosomal function, CTSB processing/activity and autophagosomal-lysosomal fusion, and blocked CTSB secretion and LAMP degradation in pkd1 knockout cells. Our data reveal for the first time a lysosomal function of PKD1 which keeps CAPN activity in check and ensures lysosomal integrity and a correct autophagic flux.Abbreviations: acCal: acetyl-calpastatin peptide; ADPKD: autosomal dominant polycystic kidney disease; CI-1: calpain inhibitor-1; CQ: chloroquine; Dox: doxycycline; EV: extracellular vesicles; EXO: exosomes; LAMP1/2: lysosomal-associated membrane protein 1/2; LGALS1/GAL1/galectin-1: lectin, galactose binding, soluble 1; LMP: lysosomal membrane permeabilization; mIMCD3: mouse inner medullary collecting duct cells; MV: microvesicles; MVB: multivesicular bodies; PAX8: paired box 8; PKD1/polycystin-1: polycystin 1, transient receptor potential channel interacting; PKD2/polycystin-2: polycystin 2, transient receptor potential cation channel; Tet: tetracycline; TFEB: transcription factor EB; VFM: vesicle-free medium; WT: wild-type.

Keywords: Autophagy; LAMPs; Pkd1; TFEB; calpains; cathepsins; lysosomes; multivesicular bodies; polycystic kidney disease; polycystin-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagy
  • Calpain* / metabolism
  • Lysosomes / metabolism
  • Mice
  • TRPP Cation Channels* / genetics
  • TRPP Cation Channels* / metabolism


  • TRPP Cation Channels
  • polycystic kidney disease 1 protein
  • Calpain

Grant support

This work was supported by the Deutsche Forschungsgemeinschaft [SFB 1140]; Deutsche Forschungsgemeinschaft [GSC-4, SGBM]; Deutsche Forschungsgemeinschaft [239283807]; Deutsche Forschungsgemeinschaft [TRR 152, ID 246781735]; Deutsche Forschungsgemeinschaft [EXC 2189 CIBSS]; Deutsche Forschungsgemeinschaft [KU 1504/5-1]; Deutsche Forschungsgemeinschaft [DFG KU 1504/7-1]; ERA-EDTA ALTF [84-2011].