| Summary: | 碩士 === 國立清華大學 === 分子與細胞生物研究所 === 99 === UNC-104/KIF1A is microtubule-dependent, neuron-specific kinesin responsible for fast axonal transport of synaptic vesicles. However, the molecular mechanism of regulating UNC-104 directional transport is not fully understood. Recent studies suggest that cargo as synaptic precursors could regulate the motor’s movements. For example, the active zone proteins SYD-2 was found to facilitate UNC-104’s motility in anterograde directions. SYD-2 binds to a specific domain at the motor’s coiled-coil region and reviewing the literature we found that another protein LIN-2 also binds to this region, therefore this protein might be also involved in motor regulation. LIN-2 is a member of the membrane-associated guanylate kinase (MAGUK) family, and its mammalian homologue of LIN-2 is CASK, multidomain scaffolding protein highly expressed in neurons. Interestingly, a previous study revealed that UNC-104 contains a MBS (MAGUK binding stalk) site, and indeed, our yeast two-hybrid assay showed that a MBS construct of UNC-104 interacts with LIN-2’s GUK domain. Interestingly, a LIN-2ΔGUK construct reveals reduced interaction with UNC-104’s MBS, but strong interaction with UNC-104’s FHA-CC2 domain, suggesting to negatively regulate the motor’s activity. In addition, the integrated SH3-GUK unit may be inhibitory for LIN-2’s interaction with the MBS while on the other hand it strongly interacts with the FHA-CC2 domain. Besides these in vitro investigations, we found that in lin-2 knockout worms, the anterograde transport of UNC-104 is reduced (displaying e.g. shorter run-lengths), while the retrograde transport (carried out by the dynein motor) is enhanced. These data implicate that loss-of-function of LIN-2 causes UNC-104 to suffer defeat in tug-of-war events between opposing motors, resulting in impaired anterograde but facilitated retrograde transport. Together, these data demonstrate a novel role for LIN-2 to directly interact with UNC-104 and to activate the motor’s motility.
|
|---|
