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

Abstract

Batten disease is characterised by lysosomal dysfunction. The most common type of the disease is caused by mutations in the membrane protein CLN3, whose function is unknown. We show that the fission yeast orthologue Btn1p, previously implicated in vacuole function, is required for correct sorting of the vacuole hydrolase carboxypeptidase Y (Cpy1p). This is, in part, due to a defect in trafficking of Vps10p, the sorting receptor for Cpy1p, from the Golgi to the trans-Golgi network in btn1Δ cells. Our data also implicate btn1 in other Vps10-independent Cpy1-sorting pathways. Furthermore, btn1 affects the number, intracellular location and structure of Golgi compartments. We show that the prevacuole location of Btn1p is at the Golgi, because Btn1p colocalises predominantly with the Golgi marker Gms1p in compartments that are sensitive to Brefeldin A. Btn1p function might be linked to that of Vps34p, a phosphatidylinositol 3-kinase, because Btn1p acts as a multicopy suppressor of the severe Cpy1p vacuole protein-sorting defect of vps34Δ cells. Together, these results indicate an important role for Btn1p in the Golgi complex, which affects Golgi homeostasis and vacuole protein sorting. We propose a similar role for CLN3 in mammalian cells.

Regulation of Ras Localization and Cell Transformation by Evolutionarily Conserved Palmitoyltransferases

“…S4B in the supplemental material). To decipher in which Golgi compartments sp-Erf2 localizes, we examined markers for two key Golgi compartments, Anp1 for the cis-Golgi compartment (46) and sp-Sec72 and Gms1 for the trans-Golgi compartment (22,46,47). Vesicles are received from the ER by the cis-Golgi compartment and can be delivered to the PM from the trans-Golgi compartment.…”

Neuronal ceroid lipofuscinosis protein CLN3 interacts with motor proteins and modifies location of late endosomal compartments

“…However, only a few molecular interactions of CLN3, related to the corresponding trafficking steps, have been reported [26,27] and, therefore, the role of CLN3 in membrane trafficking has remained unclear. CLN3 has been localised to many intracellular compartments (reviewed in [1,3,12,24]) with endosomes and lysosomes being the most prominent sites of putative CLN3 action. This view is also supported by the finding that CLN3 contains well-conserved lysosomal targeting signals recognised by adaptor proteins responsible for protein targeting downstream of the trans-Golgi network [4,48].…”

“…Trafficking abnormalities in several intracellular compartments have been reported to be due to deficiency of CLN3 or its Schizosaccharomyces pombe orthologue, Btn1p. These include impaired Golgi protein sorting [24] and exit of mannose 6-phosphate receptor from the trans-Golgi network [25], defects in endocytosis [3,26,27] and in the fast axonal transport of optic nerves [28]. Additionally, aberrant processing and delivery of lysosomal cathepsins has been suggested to result from CLN3 deficiency [3,13,25].…”

The Role of Ceroid Lipofuscinosis Neuronal Protein 5 (CLN5) in Endosomal Sorting

“…Mutations in the CLN3 gene cause juvenile NCL, more commonly known as Batten's disease. The exact function of CLN3 is still not fully elucidated; however, it was recently proposed that it affects lysosomal trafficking and sorting in yeast and mammalian cells (9,23). Moreover, ablation of CLN3 caused an accumulation of the cation-independent mannose 6-phosphate receptor (CI-MPR) lysosomal sorting receptor in the trans-Golgi network (TGN) (23), and that study found a maturation defect of the soluble lysosomal protein cathepsin D, supporting a role for CLN3 in sorting to the lysosomal compartment.…”