Biology subjects

Sobu, Y.

Publications and source records attributed to Sobu, Y..

4 recordsLinked to original sources

bioRxiv2021

Pathogenic LRRK2 control of primary cilia and Hedgehog signaling in neurons and astrocytes of mouse brain

Previously, we showed that cholinergic interneurons of the dorsal striatum lose cilia in mice harboring the Parkinsons disease associated, kinase activating, R1441C LRRK2 mutation (Dhekne et al., 2018). Here we show that this phenotype is also seen in two mouse strains carrying the most common human G2019S LRRK2 mutation. Heterozygous loss of the PPM1H phosphatase that is specific for LRRK2-phosphorylated Rab GTPases (Berndsen et al., 2019) yields the same cilia loss phenotype, strongly supporting a connection between Rab GTPase phosphorylation and cilia loss. In addition, astrocytes throughout the striatum show a ciliation defect in LRRK2 and PPM1H-/+ mutant models. Hedgehog signaling requires cilia, and loss of cilia correlates here with a loss in induction of Hedgehog signaling as monitored by in situ hybridization of Gli1 transcripts. These data support a model in which LRRK2 and PPM1H mutant mice struggle to receive and respond to critical Hedgehog signals in the nigral-striatal pathway.

cell biology↗

bioRxiv2020

Suppression of amyloid-β secretion from neurons by cis-9, trans-11-octadecadienoic acid, an isomer of conjugated linoleic acid

Conjugated linoleic acid (CLA) comprises several geometric and positional isomers of the parental linoleic acid (LA). Two of the isomers, cis-9, trans-11 CLA (c9,t11 CLA) and trans-10, cis-12 CLA (t10,c12 CLA) exert various biological activities. However, the effect of CLA on generation of neurotoxic amyloid-{beta} (A{beta}) protein remains unclear. We found that c9,t11CLA significantly suppressed generation of A{beta} in primary cultures of mouse neurons. CLA treatment did not affect the levels of {beta}-site APP-cleaving enzyme 1 (BACE1), a component of active {gamma}-secretase complex presenilin 1 amino-terminal fragment (PS1 NTF), or A{beta} protein precursor (APP) in cultured neurons. BACE1 activity in lysate of neurons treated with c9,t11 CLA, but not t10,c12 CLA, decreased slightly, although c9,t11 CLA did not directly affect the activity of recombinant BACE1. Interestingly, localization of BACE1 and APP in early endosomes increased in neurons treated with c9,t11 CLA; concomitantly, the localization of both proteins was reduced in late endosomes, where APP is predominantly cleaved by BACE1. c9,t11 CLA and t10,c12 CLA appeared to be incorporated into membrane phospholipids, as the level of CLA-containing lysophosphatidylcholine (CLA-LPC) increased dramatically in neurons incubated with CLA. Taken together, our findings indicate that accumulation of c9,t11 CLA-LPC, but not t10,c12 CLA-LPC, in neuronal membranes suppresses amyloidogenic cleavage of APP, thereby contributing to preservation of brain neurons by suppressing neurotoxic A{beta} production in aged subjects.

biochemistry↗

bioRxiv2020

LRRK2-phosphorylated Rab10 sequesters Myosin Va with RILPL2 during ciliogenesis blockade

Activating mutations in LRRK2 kinase cause Parkinsons disease. Pathogenic LRRK2 phosphorylates a subset of Rab GTPases and blocks ciliogenesis. Thus, defining novel phospho-Rab interacting partners is critical to our understanding of the molecular basis of LRRK2 pathogenesis. RILPL2 binds with strong preference to LRRK2-phosphorylated Rab8A and Rab10. RILPL2 is a binding partner of the motor protein and Rab effector, Myosin Va. We show here that the globular tail domain of Myosin Va also contains a high affinity binding site for LRRK2-phosphorylated Rab10, and certain tissue-specific Myosin Va isoforms strongly prefer to bind phosphorylated Rab10. In the presence of pathogenic LRRK2, RILPL2 relocalizes to the peri-centriolar region in a phosphoRab10- and Myosin Va-dependent manner. In the absence of phosphoRab10, expression of RILPL2 or depletion of Myosin Va increase centriolar RILPL2 levels, and either condition is sufficient to block ciliogenesis in RPE cells. These experiments show that LRRK2 generated phosphoRab10 dramatically redistributes Myosin Va-RILPL2 complexes to the mother centriole, which may sequester Myosin Va and RILPL2 in a manner that blocks their normal roles in ciliogenesis.

cell biology↗

bioRxiv2020

Pathogenic LRRK2 regulates ciliation probability upstream of Tau Tubulin kinase 2

Mutations that activate LRRK2 protein kinase cause Parkinsons disease. We have shown previously that Rab10 phosphorylation by LRRK2 enhances its binding to RILPL1 and together, these proteins block cilia formation in a variety of cell types including patient derived iPS cells. We have used live cell fluorescence microscopy to identify, more precisely, the effect of LRRK2 kinase activity on both the formation of cilia triggered by serum starvation and loss of cilia seen upon serum re-addition. LRRK2 activity decreases the overall probability of ciliation without changing the rates of cilia formation in R1441C LRRK2 MEF cells. Cilia loss in these cells is accompanied by ciliary decapitation. Kinase activity does not change the timing or frequency of decapitation or the rate of cilia loss, but increases the percent of cilia that are lost upon serum addition. LRRK2 activity, or overexpression of RILPL1 protein, blocks release of CP110 from the mother centriole, a step normally required for early ciliogenesis. In both cases, failure of CP110 uncapping was due to failure to recruit TTBK2, a kinase needed for CP110 release. In contrast, recruitment of EHD1, another step important for ciliogenesis, appears unaltered. These experiments provide critical detail to our understanding of the cellular consequences of pathogenic LRRK2 mutation, and indicate that LRRK2 blocks ciliogenesis upstream of TTBK2 and enhances the deciliation process in response to serum addition. SIGNIFICANCE STATEMENTMutations that activate LRRK2 protein kinase cause Parkinsons disease. LRRK2 phosphorylates a subset of Rab GTPases, in particular Rab8 and Rab10. Phosphorylated Rabs bind preferentially to a distinct set of effectors and block in primary ciliation in multiple cell types. We show here that the cilia blockade is upstream of the recruitment of TTBK2 kinase to the mother centriole, a step required for the release of CP110 and subsequent cilia formation. This study provides fundamental information related to how pathogenic LRRK2 interferes with normal cell physiology.

cell biology↗