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Inactivating mutations in the PPT1 gene encoding palmitoyl‐protein thioesterase‐1 (PPT1) underlie the CLN1 disease, a devastating neurodegenerative lysosomal storage disorder. The mechanism of pathogenesis underlying CLN1 disease has remained elusive. PPT1 is a lysosomal enzyme, which catalyzes the removal of palmitate from S‐palmitoylated proteins (constituents of ceroid lipofuscin) facilitating their degradation and clearance by lysosomal hydrolases. Thus, it has been proposed that Ppt1‐deficiency leads to lysosomal accumulation of ceroid lipofuscin leading to CLN1 disease. While S‐palmitoylation is catalyzed by palmitoyl acyltransferases (called ZDHHCs), palmitoyl‐protein thioesterases (PPTs) depalmitoylate these proteins. We sought to determine the mechanism by which Ppt1‐deficiency may impair lysosomal degradative function leading to infantile neuronal ceroid lipofuscinosis pathogenesis. Here, we report that in Ppt1−/− mice, which mimic CLN1 disease, low level of inositol 3‐phosphate receptor‐1 (IP3R1) that mediates Ca++ transport from the endoplasmic reticulum to the lysosome dysregulated lysosomal Ca++ homeostasis. Intriguingly, the transcription factor nuclear factor of activated T‐cells, cytoplasmic 4 (NFATC4), which regulates IP3R1‐expression, required S‐palmitoylation for trafficking from the cytoplasm to the nucleus. We identified two palmitoyl acyltransferases, ZDHHC4 and ZDHHC8, which catalyzed S‐palmitoylation of NFATC4. Notably, in Ppt1−/− mice, reduced ZDHHC4 and ZDHHC8 levels markedly lowered S‐palmitoylated NFATC4 (active) in the nucleus, which inhibited IP3R1‐expression, thereby dysregulating lysosomal Ca++ homeostasis. Consequently, Ca++‐dependent lysosomal enzyme activities were markedly suppressed. Impaired lysosomal degradative function impaired autophagy, which caused lysosomal storage of undigested cargo. Importantly, IP3R1‐overexpression in Ppt1−/− mouse fibroblasts ameliorated this defect. Our results reveal a previously unrecognized role of Ppt1 in regulating lysosomal Ca++ homeostasis and suggest that this defect contributes to pathogenesis of CLN1 disease. [ABSTRACT FROM AUTHOR]

Background: Chronic ethanol exposure causes hyperlipidemia. The present study was designed to investigate the impact of ascorbic acid supplementation on ethanol induced hyperlipidemia in testis and to compare it with that of abstinence from taking alcohol. Methods: Thirty-six male guinea pigs were divided into two groups and were maintained for 90 days as follows (1) control (C) (2) ethanol treated group (E) (4 g/kg body wt/day). Ethanol was administered for 90 days and on 90th day, alanine amino transaminase (ALT), aspartate amino transaminase (AST) and γ-glutamyltransferase (GGT) in serum was assayed. The animals in the ethanol group were further divided into an ascorbic acid supplemented group (25 mg/100 g body wt/day) (E+AA) and an ethanol abstention group (EAG) and those in the control group were divided into a control group and a control+ascorbic acid group (C+AA). Results: There was significant increase in levels of testicular cholesterol, free fatty acid, phospholipids and triglycerides in the ethanol group. There was also a significant increase in the activity of HMG CoA reductase and decrease in activity of testicular glucose-6-phosphate dehydrogenase (G6PDH) and malic enzyme in ethanol-ingested animals that further led to decreased levels of serum testosterone. Alcohol administration also enhanced the activity of testicular alcohol dehydrogenase (ADH). Ascorbic acid supplementation and abstention altered all these parameters induced by chronic alcohol administration. Histological studies were also in line with the above results. Conclusions: Ascorbic acid was able to reinstate the cholesterol homeostasis in testis which could have further restored the testicular steroidogenesis. The present study demonstrated that ascorbic acid is effective in reducing the hyperlipidemia induced by chronic alcohol administration and produced a better recovery than abstention. [ABSTRACT FROM AUTHOR]