Lipid functionalized single walled carbon nanotube-based self assembly forms a super-micellar structure. This assemblage has been exploited to trap glucose oxidase in a molecular cargo for glucose sensing. The advantage of such a molecular trap is that all components of this unique structure (both the trapping shell and the entrapped enzyme) are reusable and rechargeable. The unique feature of this sensing method lies in the solid state functionalization of single walled carbon nanotubes that facilitates liquid state immobilization of the enzyme. The method can be used for soft-immobilization (a new paradigm in enzyme immobilization) of enzymes with better thermostability that is imparted by the strong hydrophobic environment provided through encapsulation by the nanotubes.

Tunneling nanotubes (TNTs) mediate intercellular communication between animal cells in health and disease, but the mechanisms of their biogenesis and function are poorly understood. Here we report that the RNA-binding protein (RBP) nucleolin, which interacts with the known TNT-inducing protein MSec, is essential for TNT formation in mammalian cells. Nucleolin, through its RNA-binding domains (RBDs), binds to and maintains the cytosolic levels of 14-3-3ζ mRNA, and is, therefore, required for TNT formation. A specific region of the 3′-untranslated region (UTR) of the 14-3-3ζ mRNA is likely to be involved in its regulation by nucleolin. Functional complementation experiments suggest that nucleolin and 14-3-3ζ form a linear signaling axis that promotes the phosphorylation and inactivation of the F-actin depolymerization factor cofilin to induce TNT formation. MSec also similarly inactivates cofilin, but potentiates TNT formation independent of the nucleolin-14-3-3ζ axis, despite biochemically interacting with both proteins. We show that 14-3-3ζ and nucleolin are required for the formation of TNTs between primary mouse neurons and astrocytes and in multiple other mammalian cell types. We also report that the Caenorhabditis elegans orthologs of 14-3-3ζ and MSec regulate the size and architecture of the TNT-like cellular protrusions of the distal tip cell (DTC), the germline stem cell niche in the gonad. Our study demonstrates a novel and potentially conserved mRNA-guided mechanism of TNT formation through the maintenance of cellular 14-3-3ζ mRNA levels by the RBP nucleolin.

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Homeostatic scaling in neurons involve substantial proteome remodelling. Although dynamic changes to the proteome have been attributed to either translational or degradative control individually, there remains a lack of insight towards understanding how the interplay between translation and degradation modules effectuate cellular proteostasis during scaling. Here, we report that a mutual co-dependence of the two apparatus drive synaptic homeostasis in an RNA-dependent manner. We observed that abrogation of either translation or proteasomal activity prevents homeostasis and delineated the spatial features of their association. Members of the translation apparatus such as eIF4E, active forms of p70S6 kinase and miRISC-associated MOV10 were found to remain spatially linked with subunits of the catalytically active 26S proteasome subunits such as Rpt1, Rpt3, Rpt6, α7 and E3 ligase Trim32 on polysomes. We identified that paradigms of chronic downscaling involve miRISC remodelling and entails the degradation of MOV10 via the mTOR-dependent translation of Trim32. miRISC remodelling alone is sufficient to invoke downscaling through the removal of post-synaptic AMPA receptors. Our finding proposes a multifaceted model, where synaptic scaling is regulated by compositional changes in the miRISC via protein-synthesis-driven protein degradation.