Drosophila IKK-related kinase Ik2 and Katanin p60-like 1 regulate dendrite pruning of sensory neuron during metamorphosis

Abstract

Pruning is a widely observed mechanism for developing nervous systems to refine their circuitry. During metamorphosis, certain Drosophila sensory neurons undergo large-scale dendrite pruning to remove their larval branches before regeneration of their adult dendrites. Dendrite pruning involves dendrite severing, followed with debris removal. Little is known about the molecular mechanisms underlying dendrite severing. Here, we show that both the Ik2 kinase and Katanin p60-like 1 (Kat-60L1) of the Katanin family of microtubule severing proteins are required for dendrite severing. Mutant neurons with disrupted Ik2 function have diminished ability in severing their larval dendrites in pupae. Conversely, premature activation of Ik2 triggers precocious dendrite severing in larvae, revealing a critical role of Ik2 in initiating dendrite severing. We found a role for Kat-60L1 in facilitating dendrite severing by breaking microtubule in proximal dendrites, where the dendrites subsequently separate from the soma. Our study thus implicates Ik2 and Kat-60L1 in dendrite severing that involves local microtubule disassembly.Ik2/IKK ͉ microtubule severing

A novel family of katanin-like 2 protein isoforms (KATNAL2), interacting with nucleotide-binding proteins Nubp1 and Nubp2, are key regulators of different MT-based processes in mammalian cells

“…Eight adult-mouse testicles were homogenized in 50 mL of 50 mM Tris-Cl pH 7.5, 150 mM KCl, 2 mM EDTA, 0.5 % v/v Triton X-100, 19 Complete protease inhibitor (Roche) and divided in two aliquots of 25 mL (2.2 mg/mL total protein). Each aliquot was incubated overnight at 4°C with one set of beads (KATNAL2 or goat IgG), washed 3 times with lysis buffer and eluted with 2 9 20 lL of 100 mM glycine, pH 2.0.…”

“…In some invertebrates and vertebrates, additional katanin p60-like proteins (KATNAL 1 or 2) have been reported [19,20], in others, including unicellular organisms, they can be predicted from their genome sequence. Katanin p60 appears to be a multitasking enzyme implicated in an impressive number of MT-based processes (meiosis and mitosis, ciliogenesis and neurogenesis), as either a positive or negative regulator of MT polymer mass.…”

Guidance Molecules in Axon Pruning and Cell Death

“…Various intrinsic factors have been identified to regulate the pruning of axons and dendrites in Drosophila. These include the ubiquitin-proteosome system (Kuo et al 2006;Watts et al 2003), regulators of cytoskeletal dynamics (Billuart et al 2001;Lee et al 2009), caspase activities , transcription factors (Parrish et al 2007), RNAbinding proteins (Hoopfer et al 2008), proteins that hold sister chromatids together (Schuldiner et al 2008), and the FMRP protein disrupted in fragile X mental retardation (Tessier and Broadie 2008). Notably, molecular mechanisms involved in axon pruning in Drosophila share similarities with Wallerian degeneration in vertebrates.…”

Microtubule Organization and Microtubule-Associated Proteins (MAPs)

“…Other MT-related proteins, such as the plusend binding proteins CLIP-170 and CLASP2, and the minus-end binding protein CAMSAP2, are also involved in dendrite development (Beffert et al 2012;Swiech et al 2011;Yau et al 2014). Moreover, the MT-destabilizing proteins stathmin and SCLIP, or MT-severing proteins, like spastin and katanin p60-like 1, have been reported to regulate dendrite development (Jinushi-Nakao et al 2007;Lee et al 2009;Ohkawa et al 2007;Poulain et al 2008;Stewart et al 2012;Ye et al 2011). In addition, motors that drive dendritic transport are crucial for dendrite morphology (Kapitein et al 2010;Satoh et al 2008;Zheng et al 2008).…”

“…In addition to the growth and development of dendrites, MTs are needed for spine morphology and various synaptic processes, including spine formation (Shirao and Gonzalez-Billault 2013), dendritic and synaptic pruning (Kage et al 2005;Lee et al 2009;Luo and O'Leary 2005), and synaptic plasticity (Conde and Caceres 2009;Hoogenraad and Bradke 2009). MTs are abundantly present in the dendritic shaft; however, dynamic MTs can also enter actin-rich dendritic spines and regulate synaptic processes (Gu and Zheng 2009;Hu et al 2008;Jaworski et al 2009).…”