Biology subjects

Bott, C. J.

Publications and source records attributed to Bott, C. J..

4 recordsLinked to original sources

bioRxiv2026

Lipid transfer protein ORP3 mediates lysosomal repair via LC3B and ubiquitin-TAK1-p38

Lysosomal membrane damage triggers a multi-stage repair response essential for cellular homeostasis. Here we identify the oxysterol-binding protein-related protein ORP3 as a critical mediator of late-stage lysosomal membrane repair. Following lysosomal damage induced by L-leucine-leucine methyl ester (LLOME) or cationic amphiphilic drugs (CADs), ORP3 is phosphorylated and recruited to ER-lysophagosome contact sites via a signaling cascade initiated by lysosomal membrane ubiquitination, TAK1, p38 MAPK, and, to a lesser extent, IKK. p38-dependent phosphorylation promotes direct interaction between ORP3 and LC3B, which together with PI(4,5)P2 binding, is required for autophagic lysosome recruitment. ORP3 depletion impairs late-stage lysosomal recovery, elevates lysosomal lipid peroxidation, and reduces cell survival. A lipid transfer-deficient ORP3 mutant fails to restore lysosome function despite normal recruitment, indicating that ER-to-lysophagosome transfer of phosphatidylcholine by ORP3 is functionally required. ORP3 activity is subsequently terminated by VCP/p97-mediated deubiquitination of lysosomes. These findings define ORP3 as a MAPK regulated lipid transfer protein during the late autophagic phase of the endolysosomal damage response. SummaryLysosomal membrane damage triggers ubiquitination that activates a TAK1-p38 signaling cascade, phosphorylating the lipid transfer protein ORP3 and recruiting it to damaged lysosomes via LC3B interaction. ORP3-mediated phosphatidylcholine transfer from the ER is essential for late-stage lysosomal repair and cell survival. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/731146v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@b00f0borg.highwire.dtl.DTLVardef@abd2ecorg.highwire.dtl.DTLVardef@a491a2org.highwire.dtl.DTLVardef@552616_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2020

Loss of coiled-coil protein Cep55 impairs abscission processes and results in p53-dependent apoptosis in developing cortex

To produce a brain of normal size and structure, embryonic neural stem cell (NSCs) must tightly regulate their cell divisions. Cerebral cortex NSCs undergo a polarized form of cytokinesis whose regulation is poorly understood. Cytokinetic abscission severs the daughter cells and is mediated by the midbody at the apical membrane. Here we elucidate the role of the coiled-coil midbody protein Cep55 in NSC abscission and brain development. A knockout of Cep55 in mice causes microcephaly with reduced NSCs and neurons, but relatively normal body size. Fixed and live analyses show NSCs lacking Cep55 have decreased but not eliminated ESCRT recruitment, and have abnormal abscission and higher rates of failure. P53-mediated apoptosis is greatly increased in the brain, but not other tissues, and p53 knockout partly rescues brain size. Thus, loss of Cep55 causes abscission defects and failures in multiple cell types, but the secondary p53 response and apoptosis is brain-specific.

developmental biology↗

bioRxiv2019

A novel signaling role for nestin in regulating growth cone morphology via the cdk5 substrate DCX

Nestin, an intermediate filament protein widely used as a marker of neural progenitors, was recently found to be expressed transiently in developing cortical neurons in culture and in developing mouse cortex. In young cortical cultures, nestin regulates axonal growth cone morphology. In addition, nestin, which is known to bind the neuronal cdk5/p35 kinase, affects responses to axon guidance cues upstream of cdk5, specifically, to Sema3a. Changes in growth cone morphology require rearrangements of cytoskeletal networks, and changes in microtubules and actin filaments are well studied. In contrast, the roles of intermediate filament proteins in this process are poorly understood, even in cultured neurons. Here, we investigate the molecular mechanism by which nestin affects growth cone morphology and Sema3a sensitivity. We find that nestin selectively facilitates the phosphorylation of the lissencephaly-linked protein doublecortin (DCX) by cdk5/p35, but the phosphorylation of other cdk5 substrates is not affected by nestin. We uncover that this substrate selectivity is based on the ability of nestin to interact with DCX, but not with other cdk5 substrates. Nestin thus creates a selective scaffold for DCX with activated cdk5/p35. Lastly, we use cortical cultures derived from DCX knockout mice to show that the effects of nestin on growth cone morphology and on Sema3a sensitivity are DCX-dependent, thus suggesting a functional role for the DCX-nestin complex in neurons. We propose that nestin changes growth cone behavior by regulating the intracellular kinase signaling environment in developing neurons. The sex of animal subjects is unknown. Significance StatementNestin, an intermediate filament protein highly expressed in neural progenitors, was recently identified in developing neurons where it regulates growth cone morphology and responsiveness to the guidance cue Sema3a. Changes in growth cone morphology require rearrangements of cytoskeletal networks, but the roles of intermediate filaments in this process are poorly understood. We now report that nestin selectively facilitates phosphorylation of the lissencephaly-linked doublecortin (DCX) by cdk5/p35, but the phosphorylation of other cdk5 substrates is not affected. This substrate selectivity is based on preferential scaffolding of DCX, cdk5, and p35 by nestin. Additionally, we demonstrate a functional role for the DCX-nestin complex in neurons. We propose that nestin changes growth cone behavior by regulating intracellular kinase signaling in developing neurons.

cell biology↗

bioRxiv2017

Nestin in immature embryonic neurons regulates axon growth cone morphology and Sema3a sensitivity

Correct wiring in the neocortex requires that responses to an individual guidance cue vary among neurons in the same location, and within the same neuron over time. Nestin is an atypical intermediate filament expressed highly in neural progenitors and is thus used widely as a progenitor marker. Here we show a subpopulation of embryonic cortical neurons which transiently express nestin in their axons. Nestin expression is thus not restricted to neural progenitors but persists at lower levels in some newborn neurons for 2-3 days. We found that nestin-expressing neurons have smaller growth cones, suggesting that nestin affects cytoskeletal dynamics. Nestin, unlike other intermediate filament subtypes, regulates cdk5 kinase. Cdk5 activity is induced by the repulsive guidance cue Sema3a leading to growth cone collapse in vitro. Therefore, we tested whether nestin-expressing neurons showed altered responses to Sema3a. We find that nestin-expressing newborn neurons are more sensitive to Sema3a in a roscovitine-sensitive manner, whereas nestin knockdown results in lowered sensitivity to Sema3a. We propose that nestin functions in immature neurons to modulate cdk5 and thereby the Sema3a response. Thus, the transient expression of nestin could allow for temporal modulation of a neuron's response to Sema3a particularly during early axon guidance decisions.

cell biology↗