Increased expression of lysosomal acid phosphatase in CLN3‐defective cells and mouse brain tissue

Abstract

Juvenile neuronal ceroid lipofuscinosis (Batten disease) is a neurodegenerative disorder caused by defective function of the lysosomal membrane glycoprotein CLN3. The activity of the lysosomal acid phosphatase (LAP/ACP2) was found to be significantly increased in the cerebellum and brain stem of Cln3-targeted mice during the early stages of postnatal life. Histochemical localization studies revealed an increased LAP/ ACP2 staining intensity in neurons of the cerebral cortex of 48-week-old Cln3-targeted mice as compared with controls. Additionally, the expression of another lysosomal membrane protein LAMP-2 was increased in all brain areas. Knockdown of CLN3 expression in HeLa cells by RNA interference also resulted in increased LAP/ACP2 and LAMP-2 expression. The juvenile form of neuronal ceroid lipofuscinosis (JNCL, Batten disease) is a recessively inherited neurodegenerative disease of childhood which is characterized by initial gliosis and astrocytosis followed by the progressive loss of neurons in the cortex, hippocampus, cerebellum, and the retina . Clinical features include visual loss, mental and motor retardation, epilepsy, and premature death. JNCL belongs to a group of neurodegenerative diseases with defects in ten different genes encoding both soluble and polytopic membrane proteins located in either late endosomes/lysosomes or the endoplasmic reticulum The function of CLN3 is unknown and several processes have been proposed to involve the CLN3 protein such as import of arginine into lysosomes, maturation of autophagic vacuoles, vesicular trafficking, modulation of ceramide synthesis, and apoptosis (Persaud-Sawin et al. 2002, 2004Kim et al. 2003;Luiro et al. 2004;Cao et al. 2006). The role of CLN3 in lysosomal pH homeostasis has been a matter of debate depending on the cell type and model organism being studied reporting either an increase (Pearce Received April 5, 2007; Revised July 27, 2007; Accepted August 6, 2007. Address correspondence and reprint requests to Stephan Storch, Department of Biochemistry, Children's Hospital, University Medical Center Hamburg, D-20246 Hamburg, Germany. E-mail: storch@uke.uni-hamburg.deAbbrevations used: ACP2, human acid phosphatase 2; ACP5, human acid phosphatase 5; ACTB, human b-actin; ActB, mouse b-actin; JNCL, juvenile form of neuronal ceroid lipofuscinosis; LAMP-1, lysosomeassociated membrane protein 1; LAMP-2, lysosome-associated membrane protein 2; LAP, lysosomal acid phosphatase; M6P, mannose 6-phosphate; P week, postnatal week; RT, real-time; siRNA, small interfering RNA; TRAP, tartrate-resistant acid phosphatase.

S. pombe btn1, the orthologue of the Batten disease geneCLN3, is required for vacuole protein sorting of Cpy1p and Golgi exit of Vps10p

“…A thorough study of the lysosome proteome has not been performed in cells completely lacking CLN3 function. However, in JNCL cells, or in cells in which CLN3 function is substantially or partially reduced, alterations in trafficking or processing of specific lysosomal enzymes have been reported (Fossale et al, 2004;Junaid and Pullarkat, 1999;Metcalfe et al, 2008;Pohl et al, 2007;Sleat et al, 1998), and lysosomal homeostasis is affected (Holopainen et al, 2001;Kitzmüller et al, 2008;Ramirez-Montealegre and Pearce, 2005). In one instance, exit of a reporter version of the cation-independent M6PR from the TGN was significantly reduced when CLN3 was depleted (Metcalfe et al, 2008).…”

Analysis of Potential Biomarkers and Modifier Genes Affecting the Clinical Course of CLN3 Disease

“…Previously, we found that ACP2 encoding the lysosomal acid phosphatase was significantly upregulated at the mRNA and protein level in CLN3-deficient mouse brain and patient fibroblasts (9). The basal mRNA expression of ACP2 in lymphocytes, however, appears to be too low to allow detection of alterations between CLN3 patients and controls.…”

Retinal Degeneration in Mice Deficient in the Lysosomal Membrane Protein CLN7

“…Quantitative real-time PCR was performed using TaqMan gene expression assays (Applied Biosystems, Darmstadt, Germany) including predesigned probes and primers sets for mouse cathepsin D (Mm00515587_m1), cathepsin Z (Mm00517687_m1), and bactin (Mm00607939_s1). Quantitative real-time PCR was performed as described previously 44 using the Mx3000P QPCR system (Agilent Technologies, Santa Clara, CA, USA). Expression levels of the analyzed mRNAs were normalized to the amount of b-actin mRNA in the same cDNAs using the comparative CT method (2 -DDCT ).…”