Co-operative versus independent transport of different cargoes by Kinesin-1

Kinesin motors drive the intracellular transport of multiple cargoes along microtubule tracks; yet, how kinesins discriminate among their many potential cargoes is unknown. We tested whether Kinesin-1 cargoes compete, co-operate or are transported independently of each other. We focused on Kinesin-1 cargoes that bind directly to the kinesin light chain (KLC) subunit, namely the c-Jun NH₂-terminal kinase-interacting proteins (JIPs) 1 and 3, Kidins220/ARMS and PAT1. Overexpression of individual cargo proteins in differentiated CAD cells resulted in mislocalization of the endogenous protein but had no effect on localization of other cargo proteins to neurite tips. Thus, while transport of distinct cargoes is saturable, they do not compete with each other. Interestingly, we found that low expression of JIP1 or JIP3 enhanced the transport of the other JIP to neurite tips. Moreover, JIP1 and JIP3 require each other for transport. Co-operative transport is due to an interaction between JIP1 and JIP3 as well as distinct binding sites on the KLC tetratricopeptide repeat (TPR) bundle: the TPR groove binds to C-terminal residues of JIP1, whereas the TPR surface binds to internal residues in JIP3. Formation of a JIP1/JIP3/KLC complex is necessary for efficient JIP1 or JIP3 transport in neuronal cells. Thus, JIP scaffolding proteins are transported in a co-operative manner, despite the independent transport of other Kinesin-1 cargoes.     

Evaluation of the prevalence and economic burden of adverse drug reactions presenting to the medical emergency department of a tertiary referral centre: a prospective study

Background  

Adverse drug reactions (ADRs) are now recognized as an important cause of hospital admissions, with a proportion ranging from 0.9–7.9%. They also constitute a significant economic burden. We thus aimed at determining the prevalence and the economic burden of ADRs presenting to Medical Emergency Department (ED) of a tertiary referral center in India     

6-Shogaol,an active constituent of ginger,attenuates neuroinflammation and cognitive deficits in animal models of dementia

Recently, increased attention has been directed towards medicinal extracts as potential new drug candidates for dementia. Ginger has long been used as an important ingredient in cooking and traditional herbal medicine. In particular, ginger has been known to have disease-modifying effects in Alzheimer's disease (AD). However, there is no evidence of which constituents of ginger exhibit therapeutic effects against AD. A growing number of experimental studies suggest that 6-shogaol, a bioactive component of ginger, may play an important role as a memory-enhancing and anti-oxidant agent against neurological diseases. 6-Shogaol has also recently been shown to have anti-neuroinflammatory effects in lipopolysaccharide (LPS)-treated astrocytes and animal models of Parkinson’s disease, LPS-induced inflammation and transient global ischemia. However, it is still unknown whether 6-shogaol has anti-inflammatory effects against oligomeric forms of the Aβ (AβO) in animal brains. Furthermore, the effects of 6-shogaol against memory impairment in dementia models are also yet to be investigated. In this study, we found that administration of 6-shogaol significantly reduced microgliosis and astrogliosis in intrahippocampal AβO-injected mice, ameliorated AβO and scopolamine-induced memory impairment, and elevated NGF levels and pre- and post-synaptic marker in the hippocampus. All these results suggest that 6-shogaol may play a role in inhibiting glial cell activation and reducing memory impairment in animal models of dementia.     

A method for multiprotein assembly in cells reveals independent action of kinesins in complex

Teams of processive molecular motors are critical for intracellular transport and organization, yet coordination between motors remains poorly understood. Here, we develop a system using protein components to generate assemblies of defined spacing and composition inside cells. This system is applicable to studying macromolecular complexes in the context of cell signaling, motility, and intracellular trafficking. We use the system to study the emergent behavior of kinesin motors in teams. We find that two kinesin motors in complex act independently (do not help or hinder each other) and can alternate their activities. For complexes containing a slow kinesin-1 and fast kinesin-3 motor, the slow motor dominates motility in vitro but the fast motor can dominate on certain subpopulations of microtubules in cells. Both motors showed dynamic interactions with the complex, suggesting that motor–cargo linkages are sensitive to forces applied by the motors. We conclude that kinesin motors in complex act independently in a manner regulated by the microtubule track.     

Regulation of Cilium Length and Intraflagellar Transport by the RCK-Kinases ICK and MOK in Renal Epithelial Cells

Primary cilia are important sensory organelles. They exist in a wide variety of lengths, which could reflect different cell-specific functions. How cilium length is regulated is unclear, but it probably involves intraflagellar transport (IFT), which transports protein complexes along the ciliary axoneme. Studies in various organisms have identified the small, conserved family of ros-cross hybridizing kinases (RCK) as regulators of cilium length. Here we show that Intestinal Cell Kinase (ICK) and MAPK/MAK/MRK overlapping kinase (MOK), two members of this family, localize to cilia of mouse renal epithelial (IMCD-3) cells and negatively regulate cilium length. To analyze the effects of ICK and MOK on the IFT machinery, we set up live imaging of five fluorescently tagged IFT proteins: KIF3B, a subunit of kinesin-II, the main anterograde IFT motor, complex A protein IFT43, complex B protein IFT20, BBSome protein BBS8 and homodimeric kinesin KIF17, whose function in mammalian cilia is unclear. Interestingly, all five proteins moved at ∼0.45 µm/s in anterograde and retrograde direction, suggesting they are all transported by the same machinery. Moreover, GFP tagged ICK and MOK moved at similar velocities as the IFT proteins, suggesting they are part of, or transported by the IFT machinery. Indeed, loss- or gain-of-function of ICK affected IFT speeds: knockdown increased anterograde velocities, whereas overexpression reduced retrograde speed. In contrast, MOK knockdown or overexpression did not affect IFT speeds. Finally, we found that the effects of ICK or MOK knockdown on cilium length and IFT are suppressed by rapamycin treatment, suggesting that these effects require the mTORC1 pathway. Our results confirm the importance of RCK kinases as regulators of cilium length and IFT. However, whereas some of our results suggest a direct correlation between cilium length and IFT speed, other results indicate that cilium length can be modulated independent of IFT speed.     

A size-exclusion permeability barrier and nucleoporins characterize a ciliary pore complex that regulates transport into cilia

The cilium is a microtubule-based organelle that contains a unique complement of proteins for cell motility and signalling functions. Entry into the ciliary compartment is proposed to be regulated at the base of the cilium. Recent work demonstrated that components of the nuclear import machinery, including the Ran GTPase and importins, regulate ciliary entry. We hypothesized that the ciliary base contains a ciliary pore complex whose molecular nature and selective mechanism are similar to those of the nuclear pore complex. By microinjecting fluorescently labelled dextrans and recombinant proteins of various sizes, we characterize a size-dependent diffusion barrier for the entry of cytoplasmic molecules into primary cilia in mammalian cells. We demonstrate that nucleoporins localize to the base of primary and motile cilia and that microinjection of nucleoporin-function-blocking reagents blocks the ciliary entry of kinesin-2 KIF17 motors. Together, this work demonstrates that the physical and molecular nature of the ciliary pore complex is similar to that of the nuclear pore complex, and further extends functional parallels between nuclear and ciliary import.     

Tubulin modifications and their cellular functions

All microtubules are built from a basic alpha/beta-tubulin building block, yet subpopulations of microtubules can be differentially marked by a number of post-translational modifications. These modifications, conserved throughout evolution, are thought to act individually or in combination to control specific microtubule-based functions, analogous to how histone modifications regulate chromatin functions. Here we review recent studies demonstrating that tubulin modifications influence microtubule-associated proteins such as severing proteins, plus-end tracking proteins, and molecular motors. In this way, tubulin modifications play an important role in regulating microtubule properties, such as stability and structure, as well as microtubule-based functions, such as ciliary beating, cell division, and intracellular trafficking.