N-terminally truncated forms of human cathepsin F accumulate in aggresome-like inclusions

Abstract

The contribution of individual cysteine cathepsins as positive mediators of programmed cell death is dependent on several factors, such as the type of stimuli, intensity and duration of the stimulus, and cell type involved. Of the eleven human cysteine cathepsins, cathepsin F is the only cathepsin that exhibits an extended N-terminal proregion, which contains a cystatin-like domain. We predicted that the wild-type human cathepsin F contains three natively disordered regions within the enzyme's propeptide and various amino acid stretches with high fibrillation propensity. Wild-type human cathepsin F and its N-terminally truncated forms, Ala(20)-Asp(484) (Δ(19)CatF), Pro(126)-Asp(484) (Δ(125)CatF), and Met(147)-Asp(484) (Δ(146)CatF) were cloned into the pcDNA3 vector and overexpressed in HEK 293T cells. Wild-type human cathepsin F displayed a clear vesicular labeling and colocalized with the LAMP2 protein, a lysosomal marker. However, all three N-terminally truncated forms of human cathepsin F were recovered as insoluble proteins, suggesting that the deletion of at least the signal peptides (Δ(19)CatF), results in protein aggregation. Noteworthy, they concentrated large perinuclear-juxtanuclear aggregates that accumulated within aggresome-like inclusions. These inclusions showed p62-positive immunoreactivity and were colocalized with the autophagy marker LC3B, but not with the LAMP2 protein. In addition, an approximately 2-3 fold increase in DEVDase activity was not sufficient to induce apoptotic cell death. These results suggested the clearance of the N-terminally truncated forms of human cathepsin F via the autophagy pathway, underlying its protective and prosurvival mechanisms.

Cathepsins in the Pathophysiology of Mucopolysaccharidoses: New Perspectives for Therapy

“…To date, nine mutations with recessive inheritance are known to cause CLN13: six missense mutations (p.Gln321Arg, p.Gly458Ala, p.Ser480Leu, p.Tyr231Cys, p.Ile404Thr, and p.Cys326Phe), a nonsense mutation c.416C > A (p.S139*), a frameshift mutation (p.Ser319Leufs*27), and a mutation preventing the correct splicing of CTSF mRNA (c.213 + 1G>C) [134][135][136][137]. It has been shown that disease-causing CTSF mutants fail to cleave the lysosomal integral membrane protein type-2 (LIMP-2/SCARB2) required for normal biogenesis and maintenance of lysosomes and endosomes [138,139]; however, the exact mechanism by which CTSF deficiency translates in the clinical onset of CLN13 remains elusive. The biochemical and molecular mechanisms underlying NCLs have not been addressed yet.…”

Inherited diseases caused by mutations in cathepsin protease genes

“…In contrast to type 10 CLN, the stored protein is unknown . The mechanism by which mutations in this lysosomal cysteine protease (MEROPS ID: C01.018) gene, which is mainly associated with lysosomal degradation and autophagy , cause this adult‐onset CLN is completely obscure. In any case, the slow progression of the disease argues for a mild effect on CTSF function or for a partial compensation of its loss‐of‐function.…”

Alu-Derived Alternative Splicing Events Specific to Macaca Lineages in CTSF Gene

“…Human CTSF propeptide consists of a signal peptide, a cystatin-like domain, an I29 inhibitor domain, and a mature form of cathepsin F (Jeric et al, 2013). Previous studies have revealed the cysteine-cathepsin-related activation of programmed cell death (apoptosis) (Guicciardi et al, 2004; Repnik et al, 2012), but the physiological functions of CTSF have not been thoroughly investigated.…”

“…In the human genome, 11 different cysteine cathepsins have been characterized (cathepsins B, C, F, H, K, L, O, S, V, X, and W) via bioinformatics analysis (Rossi et al, 2004). Among them, CTSF has an extended N-terminal proregion, which contains a cystatin-like domain (Ahn et al, 2009; Jeric et al, 2013). Similar to cathepsins B, C, H, L, O, and Z, CTSF is ubiquitously expressed in widespread tissues, whereas cathepsins J, K, S, and W are expressed in restricted tissues or cell types (Tang et al, 2006; Turk et al, 2012).…”