Enzyme replacement therapy with recombinant pro-CTSD (cathepsin D) corrects defective proteolysis and autophagy in neuronal ceroid lipofuscinosis

Abstract

CTSD (cathepsin D) is one of the major lysosomal proteases indispensable for the maintenance of cellular proteostasis by turning over substrates of endocytosis, phagocytosis and autophagy. Consequently, CTSD deficiency leads to a strong impairment of the lysosomal-autophagy machinery. In mice and humans CTSD dysfunction underlies the congenital variant (CLN10) of neuronal ceroid lipofuscinosis (NCL). NCLs are distinct lysosomal storage disorders (LSDs) sharing various hallmarks, namely accumulation of protein aggregates and ceroid lipofuscin leading to neurodegeneration and blindness. The most established and clinically approved approach to treat LSDs is enzyme replacement therapy (ERT) aiming to replace the defective hydrolase with an exogenously applied recombinant protein. Here we reveal that recombinant human pro-CTSD produced in a mammalian expression system can be efficiently taken up by a variety of cell models, is correctly targeted to lysosomes and processed to the active mature form of the protease. In proof-of-principle experiments we provide evidence that recombinant human CTSD (rhCTSD) can improve the biochemical phenotype of CTSDdeficient hippocampal slice cultures in vitro and retinal cells in vivo. Furthermore, we demonstrate that dosing of rhCTSD in the murine CLN10 model leads to a correction of lysosomal hypertrophy, storage accumulation and impaired autophagic flux in the viscera and central nervous system (CNS). We establish that direct delivery of the recombinant protease to the CNS is required for improvement of neuropathology and lifespan extension. Together these data support the continuation of the pre-clinical studies for the application of rhCTSD in the treatment of NCL.

Molecular networking in the neuronal ceroid lipofuscinoses: insights from mammalian models and the social amoeba Dictyostelium discoideum

“…Additionally, several NCL disease models display aberrant autophagy, which has also been reported in other forms of neurodegeneration [110]. In fact, previous work has linked the functions of 10 of the 13 NCL proteins to autophagic mechanisms (PPT1/CLN1, TPP1/CLN2, CLN3, CLN5, CLN6, MFSD8/CLN7, CTSD/CLN10, PGRN/ CLN11, ATP13A2/CLN12, KCTD7/CLN14) [111][112][113][114][115][116][117][118][119][120].…”

TFEB Transcriptional Responses Reveal Negative Feedback by BHLHE40 and BHLHE41

“…The magnitude of expression of these genes did not change in response to nuclear-localized TFEB or Torin treatment, suggesting that their enhancer motif is highly accessible and requires low levels of nuclear TFEB for activation. Furthermore, deficiencies in the lysosomal protease and classical complement component genes are associated with lysosomal storage, neurodegenerative, and autoimmune diseases (Butler et al, 2019;Lintner et al, 2016;Macedo and Isaac, 2016;Marques et al, 2020;Nakajima et al, 2019;Prada et al, 2014;Tang et al, 2006). Thus, cells likely require a constant level of transcription of these innate immune response genes to maintain homeostasis or rapidly respond to exogenous stimuli.…”

Inhibition of Cathepsin D (CTSD) enhances radiosensitivity of glioblastoma cells by attenuating autophagy

“…Overall, it is acknowledged that CTSD can inhibit damage-induced cell death, such as oxidative stress or acetate, in an autophagy dependent 20 tem. 39 CTSD inhibitor may also be a potential drug to improve the radiotherapeutic efficacy of patients with GBM. Of course, more in vivo and clinical trials are needed to prove this.…”