Plectin dysfunction in neurons leads to tau accumulation on microtubules affecting neuritogenesis, organelle trafficking, pain sensitivity and memory.

AIMS: Plectin, a universally expressed multi-functional cytolinker protein, is crucial for intermediate filament networking, including crosstalk with actomyosin and microtubules. In addition to its involvement in a number of diseases affecting skin, skeletal muscle, heart, and other stress-exposed tissues, indications for a neuropathological role of plectin have emerged. Having identified P1c as the major isoform expressed in neural tissues in previous studies, our aim for the present work was to investigate whether, and by which mechanism(s), the targeted deletion of this isoform affects neuritogenesis and proper nerve cell functioning. METHODS: For ex vivo phenotyping, we used dorsal root ganglion and hippocampal neurons derived from isoform P1c-deficient and plectin-null mice, complemented by in vitro experiments using purified proteins and cell fractions. To assess the physiological significance of the phenotypic alterations observed in P1c-deficient neurons, P1c-deficient and wild-type littermate mice were subjected to standard behavioural tests. RESULTS: We demonstrate that P1c affects axonal microtubule dynamics by isoform-specific interaction with tubulin. P1c deficiency in neurons leads to altered dynamics of microtubules and excessive association with tau protein, affecting neuritogenesis, neurite branching, growth cone morphology, and translocation and directionality of movement of vesicles and mitochondria. On the organismal level, we found P1c deficiency manifesting as impaired pain sensitivity, diminished learning capabilities and reduced long-term memory of mice. CONCLUSIONS: Revealing a regulatory role of plectin scaffolds in microtubule-dependent nerve cell functions, our results have potential implications for cytoskeleton-related neuropathies.

Inhibition of 2'-5' oligoadenylate synthetase by divalent metal ions.

OAS1 is the small form and OAS2 is the medium form of the human interferon-induced 2'-5' oligoadenylate synthetases. The p42 isoform of OAS1 and the p69 isoform of OAS2 have been expressed in insect cells and purified to give pure, highly active 2'-5' oligoadenylate synthetase. The catalysis of 2'-5' oligoadenylate synthesis is strictly dependent on double-stranded RNA and magnesium ions. We have examined the effect of a series of divalent metal ions: copper, iron and zinc ions strongly inhibited the enzymatic activity, cobalt and nickel ions were partly inhibitory whereas calcium and manganese ions were without effect. However, manganese ions can replace magnesium ions as activator. The inhibitory effect of zinc ions was characterised in detail. The inhibitory constants of Zn(2+) were estimated to be 0.10 mM for OAS1p42 and to 0.02 mM for OAS2p69. Cross-linking experiments showed that zinc ions can control the oligomerisation by enhancing the formation of tetrameric forms of OAS1p42