Biomedical subjects

Anu Jalanko

Publications and source records attributed to Anu Jalanko.

21 records · Page 2Linked to original sources

PubMed2002

Lysosomal localization of the neuronal ceroid lipofuscinosis CLN5 protein.

The Finnish variant late infantile neuronal ceroid lipofuscinosis (vLINCL) belongs to the neuronal ceroid lipofuscinosis group of common recessively inherited neurodegenerative disorders. The CLN 5 gene responsible for this brain disorder codes for a novel protein with no homology to previously reported proteins. In this study, we have investigated the biosynthesis and intracellular localization of this protein in transiently transfected BHK-21 cells using a CLN5-specific peptide antibody. Confocal immunofluorescence microscopy showed that wild-type CLN5 is predominantly targeted to lysosomes and immunoprecipitation analysis recognized a 60 kDa polypeptide. The molecular weight of this protein was reduced to 40 kDa by deglycosylation with Endo H and to 38 kDa with PNGase F. The same-sized glycosylated polypeptides were also observed in the media, suggesting that the 60 kDa glycosylated CLN5 polypeptide represents a soluble lysosomal glycoprotein, not an integral transmembrane protein as predicted earlier. The most common human vLINCL mutation blocked the lysosomal targeting of expressed polypeptides. This would imply that the pathogenesis of vLINCL would be associated with the defective lysosomal trafficking, preventing the normal biological function of the corresponding polypeptide.

Cell Line↗

PubMed2002

Neuronal ceroid lipofuscinoses are connected at molecular level: interaction of CLN5 protein with CLN2 and CLN3.

Neuronal ceroid lipofuscinoses (NCLs) are neurodegenerative storage diseases characterized by mental retardation, visual failure, and brain atrophy as well as accumulation of storage material in multiple cell types. The diseases are caused by mutations in the ubiquitously expressed genes, of which six are known. Herein, we report that three NCL disease forms with similar tissue pathology are connected at the molecular level: CLN5 polypeptides directly interact with the CLN2 and CLN3 proteins based on coimmunoprecipitation and in vitro binding assays. Furthermore, disease mutations in CLN5 abolished interaction with CLN2, while not affecting association with CLN3. The molecular characterization of CLN5 revealed that it was synthesized as four precursor forms, due to usage of alternative initiator methionines in translation. All forms were targeted to lysosomes and the longest form, translated from the first potential methionine, was associated with membranes. Interactions between CLN polypeptides were shown to occur with this longest, membrane-bound form of CLN5. Both intracellular targeting and posttranslational glycosylation of the polypeptides carrying human disease mutations were similar to wild-type CLN5.

Aminopeptidases↗

PubMedDate not supplied

Unraveling the molecular pathogenesis of free sialic acid storage disorders: altered targeting of mutant sialin.

Salla disease (SD) and infantile sialic acid storage disease (ISSD) are recessively inherited, neuro-degenerative disorders caused by mutations in the SLC17A5 gene. The gene product, sialin, is a lysosomal membrane protein which transports free sialic acid across the membrane. Although the function of sialin is basically known, the details of biosynthesis and intracellular trafficking as well as functional consequences of disease mutations in the SLC17A5 gene are not characterized. Here we studied for the first time the expression, localization, and targeting of the wild-type sialin as well as two mutant polypeptides; one mimicking the Finnish founder mutation, R39C (Salla(FIN)), and the other a deletion (del268-272) found in ISSD patients using in vitro expression of the corresponding cDNA constructs. The wild-type sialin was targeted to lysosomes whereas a significant fraction of the Salla(FIN) polypeptides and the majority of the ISSD polypeptides remained in the Golgi compartment. Further, using a temperature block of intracellular transport, we observed that the rate of the trafficking of the mutant polypeptides to lysosomes is significantly slower than that of their wild-type counterpart. These findings are in line with the phenotypic differences between SD and ISSD, the former presenting mental retardation with long life span in contrast to the latter being an early fatal disorder.

Animals↗