KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family

Potassium Channel Tetramerization Domain 5 (KCTD5) regulates diverse aspects of physiology, ranging from neuronal signaling to colorectal cancer. A key feature of KCTD5 is its self-assembly into multi-subunit oligomers that seemingly enables participation in an array of protein-protein interactions. KCTD5 has recently been reported to form hetero-oligomeric complexes with two similar KCTDs (KCTD2 and KCTD17). However, it is not known if KCTD5 forms hetero-oligomeric complexes with the remaining KCTD protein family which contains over two dozen members. Here, we demonstrate that KCTD5 interacts with various KCTD proteins when assayed through co-immunoprecipitation in lysed cells. We reinforced this dataset by examining KCTD5 interactions in a live-cell bioluminescence resonance energy transfer (BRET)-based approach. Finally, we developed an IP-luminescence approach to map regions on KCTD5 required for interaction with a selection of KCTD that have established roles in neuronal signaling. We report that different regions on KCTD5 are responsible for uniquely contributing to interactions with other KCTD proteins. While our results help unravel additional interaction partners for KCTD5, they also reveal additional complexities in KCTDs' biology. Moreover, our findings also suggest that KCTD hetero-oligomeric interactions may occur throughout the KCTD family.

Customizable Open-Source Rotating Rod (Rotarod) Enables Robust Low-Cost Assessment of Motor Performance in Mice

Reliable measurements of motor learning and coordination in mice are fundamental aspects of neuroscience research. Despite the advent of deep-learning approaches for motor assessment, performance testing on a rotating rod (rotarod) has remained a staple in the neuroscientist's toolbox. Surprisingly, commercially available rotarod instruments offer limited experimental flexibility at a relatively high cost. In order to address these concerns, we engineered a highly-customizable, low-budget rotarod device with increased functionality. Here, we present a detailed guide to assemble this rotarod using simple materials. Our apparatus incorporates a variation of interchangeable rod sizes and designs which provides for adjustable testing sensitivity. Moreover, our rotarod is driven by open-source software enabling bespoke acceleration ramps and sequences. Finally, we report the strengths and weaknesses of each rod design following multiday testing on cohorts of C57BL/6 mice. We expect explorations in deviant rod types to provide a foundation for the development of increasingly sensitive models for motor performance testing along with low-budget alternatives for the research community.

Protein kinase C-dependent and Ca2+-dependent mechanisms of secretion from streptolysin O-permeabilized platelets: effects of leakage of cytosolic proteins

Human platelets containing dense granules labelled with 5-hydroxy[14C]tryptamine ([14C]5-HT) were permeabilized by exposure to streptolysin O (SLO) in the presence of 4 mM [gamma-32P]ATP. Addition of either 100 nM phorbol 12-myristate 13-acetate (PMA) or of Ca2+ (pCa 5) at the same time as SLO induced secretion of dense-granule [14C]5-HT and the phosphorylation of pleckstrin by protein kinase C (PKC). Ca2+ also induced phosphorylation of myosin P-light chains. Guanosine 5'-[gamma-thio]triphosphate (GTP[S], 100 microM) did not stimulate secretion from SLO-permeabilized platelets in the absence of Ca2+ (pCa>9), but greatly potentiated secretion in the presence of low PMA (10 nM) or low Ca2+ (pCa 6). However, GTP[S] did stimulate myosin P-light-chain phosphorylation in the absence of Ca2+, an effect that was associated with morphological changes, including granule centralization. Inhibition of PKC and of pleckstrin phosphorylation by Ro 31-8220 blocked secretion induced by PMA or by GTP[S] and PMA in the absence of Ca2+, but did not prevent the GTP[S]-induced phosphorylation of myosin P-light chains or secretion induced by Ca2+ at pCa 5. When the time period between exposure of platelets to SLO and challenge at pCa>9 with PMA or with GTP[S] and PMA was increased, there were rapid and parallel decreases in the secretion and pleckstrin phosphorylation responses, which were lost after 3-5 min. In contrast, the responsiveness of secretion to Ca2+ (pCa 5) or to GTP[S] and Ca2+ (pCa 6) persisted for at least 10 min after exposure of platelets to SLO, although the ability of pleckstrin to undergo phosphorylation was still lost after 3-5 min. Both PKC and pleckstrin were undetectable within platelets after 5 min exposure to SLO. The results suggest that the loss of responsiveness to PMA or to GTP[S] and PMA is attributable to the leakage of PKC (and possibly pleckstrin) from the platelets, whereas secretion stimulated by Ca2+ or by GTP[S] and Ca2+ utilizes membrane-associated Ca2+- and GTP-binding proteins and occurs independently of PKC activation.