Hybrid proline-rich proteins: novel players in plant cell elongation?

BACKGROUND AND AIMS: Hybrid proline-rich proteins (HyPRPs) represent a large family of putative cell-wall proteins characterized by the presence of a variable N-terminal domain and a conserved C-terminal domain that is related to non-specific lipid transfer proteins. The function of HyPRPs remains unclear, but their widespread occurrence and abundant expression patterns indicate that they may be involved in a basic cellular process. METHODS: To elucidate the cellular function of HyPRPs, we modulated the expression of three HyPRP genes in tobacco (Nicotiana tabacum) BY-2 cell lines and in potato (Solanum tuberosum) plants. KEY RESULTS: In BY-2 lines, over-expression of the three HyPRP genes with different types of N-terminal domains resulted in similar phenotypic changes, namely increased cell elongation, both in suspension culture and on solid media where the over-expression resulted in enhanced calli size. The over-expressing cells showed increased plasmolysis in a hypertonic mannitol solution and accelerated rate of protoplast release, suggesting loosening of the cell walls. In contrast to BY-2 lines, no phenotypic changes were observed in potato plants over-expressing the same or analogous HyPRP genes, presumably due to more complex compensatory mechanisms in planta. CONCLUSIONS: Based on the results from BY-2 lines, we propose that HyPRPs, more specifically their C-terminal domains, represent a novel group of proteins involved in cell expansion.

Treatment of cataplexy in Niemann-Pick disease type C with the use of miglustat.

Cataplexy is the sudden muscle weakness brought on by strong emotions, particularly joking, laughter, or anger. Cataplexy may involve only certain group of muscles or the entire voluntary musculature. In rare cases, symptoms of cataplexy can be seen during the course of some inherited diseases (Niemann-Pick type C (NPC), Prader-Willi syndrome, myotonic dystrophy, Norrie disease). We report the successful use of miglustat, a reversible inhibitor of the enzyme glucosylceramide synthase, approved for use in Gaucher's disease, and which catalyses the first step in the biosynthesis of most glycosphingolipid, in a boy with NPC with cataplexy. A 9-year-old boy was admitted for assessments of frequent "drop attacks" while laughing. The filipin fluorescence tests of cultured skin fibroblasts revealed massive accumulation of unesterified cholesterol, confirming the diagnosis of NPC disease. Molecular studies confirmed the diagnosis of NPC too. After approval from the bioethics committee, miglustat was initiated on the child at 100mg three times a day. Cataplectic attacks disappeared completely after 6 months on treatment, and patient continues to be in remission from the cataplectic attacks at 16 months follow-up. There was no further progression of neurological signs or symptoms or splenomegaly, with some improvement in cognitive function as well as social, affective and attention problems, up-gaze, and gait. Miglustat was well tolerated with no side effects observed. In summary, this is the first report of miglustat treatment of cataplexy in NPC. Long-term follow-up for continuing efficacy and tolerability in a larger cohort with NPC is needed to substantiate our observation.