Luo, S. et al. (2017) International Worm Meeting "Regulation of neurogenesis by stress."

Luo, S., Horvitz, B.

[International Worm Meeting, 2017]

Unlike most neurons, which are derived from ectoderm, the C. elegans pharyngeal I4 neuron is generated from a mesodermal cell lineage. We found that efficient generation of I4 is dependent on HLH-3, the C. elegans homolog of the mammalian proneural protein Mash1, and the Mediator CDK-8 kinase complex (DPY-22, LET-19, CDK-8, CIC-1), which is conserved throughout evolution. HLH-3 and the CDK-8 Mediator function synergistically to promote efficient I4 neurogenesis. Recently we discovered that I4 neurogenesis is also modulated by environmental stresses, such as DMSO or ethanol. We found that DMSO and ethanol induce endoplasmic reticulum (ER) stress, as they elicit expression of hsp-4p::gfp, an ER stress reporter, but not of the mitochondria stress reporter hsp-6p::gfp or the cytosolic stress reporter hsp-16.2p::gfp. DMSO and ethanol each enhance I4 loss in hlh-3 but not in Mediator mutants, suggesting that DMSO and ethanol-induced stresses might function by suppressing CDK-8 Mediator function. Interestingly, we found that the p38 MAPK innate immunity pathway is required for DMSO and ethanol to suppress I4 neurogenesis. We hypothesize that DMSO or ethanol activates the p38 MAPK pathway, which suppresses I4 neurogenesis by inhibiting the CDK-8 Mediator function. Since in mammals the p38 MAPK pathway has been implicated in inflammation and neurodegeneration, by identifying the molecular mechanisms by which the p38 MAPK pathway regulates I4 neurogenesis, we hope to generate novel insights into the mechanisms of stress-induced neurogenesis defects and neuropathology.

Luo S et al. (1996) East Coast Worm Meeting "Analysis of the MEC-3 LIM domain"

Luo S, Chalfie M

[East Coast Worm Meeting, 1996]

MEC-3 has two LIM domains(LIM1, LIM2), that are required for MEC3 function. Mutation of either LIM domain [ MEC-3LIM1 (Cys53Ser, Cys56Ala) or MEC-3 LIM2 (Cys1 17Ala, Cys118Ala, Cys121Ser)] results in proteins that rescued the tail sensitivity of the mec3 (e1338) mutants, while the double mutant (MEC-3 LIM1,2) failed to rescue mec-3 (e1338). The fragment of mec-3 encoding aa27153 (containing the two LIM domains) was cloned into the GAL4 DNA binding vector PAST, and two million clones were screened for yeast two hybrid interactions using cDNA library provided by Bob Barstead. 204 positive clones were recovered. Among them, 135 clones (represented by clone 52) encode a histidine-rich protein, and 5 clones (represented by clone 56) encode another novel protein. A single clone ( 6-13 ) encodes a leucinezipper protein, and another (16-1) encodes the C. elegans homolog of TFIIH. In vitro GST binding study showed that the GST fusion proteins of 5-2, 5-6, 16-1 can interact with in vitro translated full length MEC3 protein, which confirmed the data in yeast. We haven't been able to express a GST fusion of the 6-13 protein. We have made both GFP and galactosidase fusion protein with 5-6 and 6-13. The 5-6 fusions are expressed in the six touch cells and many other cells, while 6-13 is expressed in many cells (including some ventral motor neurons), but not in the touch cells. Sequence analysis of the remaining positive clones is on going. Further experiments will focus on the in vivo significance of the interactions of these proteins with MEC-3.

Luo S et al. (2011) Genesis "Caenorhabditis elegans reproductive aging: Regulation and underlying mechanisms."

Murphy CT, Luo S

[Genesis, 2011]

Female reproductive decline is one of the first aging phenotypes in humans, manifested in increasing rates of infertility, miscarriage, and birth defects in children of mothers over 35. Recently, Caenorhabditis elegans (C. elegans) has been developed as a model to study reproductive aging, and several studies have advanced our knowledge of reproductive aging regulation in this organism. In this review, we describe our current understanding of reproductive cessation in C. elegans, including the relationship between oocyte quality, ovulation rate, progeny number, and reproductive span. We then discuss possible mechanisms of oocyte quality control, and provide an overview of the signaling pathways currently identified to be involved in reproductive span regulation in C. elegans. Finally, we extend the relevance of C. elegans reproductive aging studies to the issue of human female reproductive decline, and we discuss ideas concerning the relationship between reproductive aging and somatic longevity.

Luo S et al. (2006) J Biol "Regulators of kinesin involved in polarized trafficking and axon outgrowth."

Nonet ML, Luo S

[J Biol, 2006]

ABSTRACT : Proteins such as UNC-76 that associate with kinesin motors are important in directing neurite extension. A small Caenorhabditis elegans coiled-coil protein, UNC-69, has now been shown to interact with UNC-76 and to be involved in axonal (but not dendritic) transport and outgrowth, as well as synapse formation.

Luo S et al. (2017) Curr Biol "The CDK8 Complex and Proneural Proteins Together Drive Neurogenesis from a Mesodermal Lineage."

Horvitz HR, Luo S

[Curr Biol, 2017]

At least some animal species can generate neurons from mesoderm or endoderm, but the underlying mechanisms remain unknown. We screened for C.elegans mutants in which the presumptive mesoderm-derived I4 neuron adopts a muscle-like cell fate. From this screen, we identified HLH-3, the C.elegans homolog of a mammalian proneural protein (Ascl1) used for invitro neuronal reprogramming, as required for efficient I4 neurogenesis. We discovered that the CDK-8 Mediator kinase module acts together with a second proneural protein, HLH-2, and in parallel to HLH-3 to promote I4 neurogenesis. Genetic analysis revealed that CDK-8 most likely promotes I4 neurogenesis by inhibiting the CDK-7/CYH-1 (CDK7/cyclin H) kinase module of the transcription initiation factor TFIIH. Ectopic expression of HLH-2 and HLH-3 together promoted expression of neuronal features in non-neuronal cells. These findings reveal that the Mediator CDK8 kinase module can promote non-ectodermal neurogenesis and suggest that inhibiting CDK7/cyclin H might similarly promote neurogenesis.

Luo S et al. (2018) Curr Opin Struct Biol "Structural biology of the separase-securin complex with crucial roles in chromosome segregation."

Luo S, Tong L

[Curr Opin Struct Biol, 2018]

The cysteine protease separase opens the cohesin ring by cleaving its kleisin subunit and is a pivotal cell cycle factor for the transition from metaphase to anaphase. It is inhibited by forming a complex with the chaperone securin, and in vertebrates, also by the Cdk1-cyclin B1 complex. Separase is activated upon the destruction of securin or cyclin B1 by the proteasome, after ubiquitination by the anaphase-promoting complex/cyclosome (APC/C). Here we review recent structures of the active protease segment of Chaetomium thermophilum separase in complex with a substrate-mimic inhibitor and full-length Saccharomyces cerevisiae and Caenorhabditis elegans separase in complex with securin. These structures define the mechanism for substrate recognition and catalysis by separase, and show that securin has extensive contacts with separase, consistent with its chaperone function. They confirm that securin inhibits separase by binding as a pseudo substrate.

Luo S et al. (2010) Cell "TGF- and insulin signaling regulate reproductive aging via oocyte and germline quality maintenance."

Luo S, Kleemann GA, Murphy CT, Shaw WM, Ashraf JM

[Cell, 2010]

Reproductive cessation is perhaps the earliest aging phenotype that humans experience. Similarly, reproduction of Caenorhabditis elegans ceases in mid-adulthood. Although somatic aging has been studied in both worms and humans, mechanisms regulating reproductive aging are not yet understood. Here, we show that TGF- Sma/Mab and Insulin/IGF-1 signaling regulate C. elegans reproductive aging by modulating multiple aspects of the reproductive process, including embryo integrity, oocyte fertilizability, chromosome segregation fidelity, DNA damage resistance, and oocyte and germline morphology. TGF- activity regulates reproductive span and germline/oocyte quality noncell-autonomously and is temporally and transcriptionally separable from its regulation of growth. Chromosome segregation, cell cycle, and DNA damage response genes are upregulated in TGF- mutant oocytes, decline in aged mammalian oocytes, and are critical for oocyte quality maintenance. Our data suggest that C. elegans and humans share many aspects of reproductive aging, including the correlation between reproductive aging and declining oocyte quality and mechanisms determining oocyte quality.

Luo S et al. (2014) Development "The conserved LIM domain-containing focal adhesion protein ZYX-1 regulates synapse maintenance in Caenorhabditis elegans."

Schaefer AM, Nonet ML, Luo S, Dour S

[Development, 2014]

We describe the identification of zyxin as a regulator of synapse maintenance in mechanosensory neurons in C. elegans. zyx-1 mutants lacked PLM mechanosensory synapses as adult animals. However, most PLM synapses initially formed during development but were subsequently lost as the animals developed. Vertebrate zyxin regulates cytoskeletal responses to mechanical stress in culture. Our work provides in vivo evidence in support of such a role for zyxin. In particular, zyx-1 mutant synaptogenesis phenotypes were suppressed by disrupting locomotion of the mutant animals, suggesting that zyx-1 protects mechanosensory synapses from locomotion-induced forces. In cultured cells, zyxin is recruited to focal adhesions and stress fibers via C-terminal LIM domains and modulates cytoskeletal organization via the N-terminal domain. The synapse-stabilizing activity was mediated by a short isoform of ZYX-1 containing only the LIM domains. Consistent with this notion, PLM synaptogenesis was independent of -actinin and ENA-VASP, both of which bind to the N-terminal domain of zyxin. Our results demonstrate that the LIM domain moiety of zyxin functions autonomously to mediate responses to mechanical stress and provide in vivo evidence for a role of zyxin in neuronal development.

Luo S et al. (2009) PLoS Genet "TGF-beta Sma/Mab signaling mutations uncouple reproductive aging from somatic aging."

Shaw WM, Murphy CT, Ashraf J, Luo S

[PLoS Genet, 2009]

Female reproductive cessation is one of the earliest age-related declines humans experience, occurring in mid-adulthood. Similarly, Caenorhabditis elegans' reproductive span is short relative to its total life span, with reproduction ceasing about a third into its 15-20 day adulthood. All of the known mutations and treatments that extend C. elegans' reproductive period also regulate longevity, suggesting that reproductive span is normally linked to life span. C. elegans has two canonical TGF-beta signaling pathways. We recently found that the TGF-beta Dauer pathway regulates longevity through the Insulin/IGF-1 Signaling (IIS) pathway; here we show that this pathway has a moderate effect on reproductive span. By contrast, TGF-beta Sma/Mab signaling mutants exhibit a substantially extended reproductive period, more than doubling reproductive span in some cases. Sma/Mab mutations extend reproductive span disproportionately to life span and act independently of known regulators of somatic aging, such as Insulin/IGF-1 Signaling and Dietary Restriction. This is the first discovery of a pathway that regulates reproductive span independently of longevity and the first identification of the TGF-beta Sma/Mab pathway as a regulator of reproductive aging. Our results suggest that longevity and reproductive span regulation can be uncoupled, although they appear to normally be linked through regulatory pathways.

Luo S et al. (2019) Molecules "In Vivo and In Vitro Antioxidant Activities of Methanol Extracts from Olive Leaves on Caenorhabditis elegans."

Jiang X, Yang Q, Ding C, Jia L, Du Y, Luo S, Li M, Tan C

[Molecules, 2019]

The aim of this study was to evaluate the antioxidant activities of extracts from olive leaves (EOL). The main contents of EOL were determined by colorimetric methods. The antioxidant activities were assessed by measuring the scavenging free radicals in vitro. To investigate the antioxidant activity in vivo, we detected the survival of <i>Caenorhabditis elegans</i>, under thermal stress. Subsequently the reactive oxygen species (ROS) level, activities of antioxidant enzymes, the expression of HSP-16.2 and the translocation of <i>daf-16</i> were measured. The results showed that, polyphenols was the main component. EOL could well scavenge DPPH and superoxide anion radicals in vitro. Compared to the control group, the survival rate of <i>C. elegans</i> treated with EOL was extended by 10.43%, under heat stress. The ROS level was reduced, while the expression of <i>hsp-16.2</i> was increased to protect the organism against the increasing ROS. The level of malondialdehyde (MDA) also decreased sharply. The activities of inner antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) were potentiated, which might have had a correlation with the DAF-16 transcription factor that was induced-turned into the nuclear. Therefore, EOL showed a strong antioxidant ability in vitro and in vivo. Hence, it could be a potential candidate when it came to medicinal and edible plants.