Biology subjects

Shirolikar, S.

Publications and source records attributed to Shirolikar, S..

3 recordsLinked to original sources

bioRxiv2020

Heterotrimeric kinesin-2 motor subunit, KLP68D, localises Drosophila odour receptor coreceptor in the distal domain of the olfactory cilia

Ciliary localisation of the odour receptor coreceptor (Orco) is essential for insect olfaction. Here, we show that in the Drosophila antenna Orco enters the bipartite cilia expressed on the olfactory sensory neurons in two discrete, one-hour intervals after the adult eclosion. Genetic analyses suggest that the heterotrimeric kinesin-2 is essential for Orco transfer from the base into the cilium. Using in vitro pulldown assay, we show that Orco binds to the C-terminal tail domain of KLP68D, the {beta}-subunit of kinesin-2. Reduced Orco enrichment decreases electrophysiological response to odours and loss of olfactory behaviour. Finally, we show that kinesin-2 function is necessary to compact Orco to an approximately four-micron stretch at the distal portion of the ciliary outer-segment bearing singlet microtubule filaments. Altogether, these results highlight an independent, tissue-specific regulation of Orco entry at specific developmental stages and its localisation to a ciliary subdomain by kinesin-2. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=199 SRC="FIGDIR/small/395905v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@177d376org.highwire.dtl.DTLVardef@1dc14d6org.highwire.dtl.DTLVardef@1dc2d21org.highwire.dtl.DTLVardef@16e90c_HPS_FORMAT_FIGEXP M_FIG C_FIG Author SummaryJana, Jain, Dutta et al., show that the odour receptor coreceptor only enters the cilia expressed on olfactory sensory neurons at specified developmental stages requiring heterotrimeric kinesin-2. The motor also helps to localise the coreceptor in a compact, environment-exposed domain at the ciliary outer-segment. HighlightsO_LIOdorant receptor coreceptor (Orco) selectively enters the olfactory cilia. C_LIO_LIOrco localises in a specific domain at the distal segment of the olfactory cilium. C_LIO_LIOrco/ORx binds to the C-terminal tail domain of the kinesin-2{beta} motor subunit. C_LIO_LIOrco entry across the transition zone and its positioning require Kinesin-2. C_LI

cell biology↗

bioRxiv2020

Nanoscale indentation of plasma membrane establishes a contractile actomyosin scaffold through selective activation of the Amphiphysin-Rho1-Dia/DAAM and Rok pathway

Nanoscale bending of plasma membrane increases cell adhesion, induces cell-signalling, triggers F-actin assembly and endocytosis in tissue-cultured cells. The underlying mechanisms are not very well understood. Here, we show that stretching the plasma membrane of somatic cyst cell around rigid spermatid heads generates a stable, tubular endomembrane scaffold supported by contractile actomyosin. The structure resembles an actin-basket covering the bundle of spermatid heads. Genetic analysis suggests that the actomyosin organisation is nucleated exclusively by the Formins, Diaphanous and DAAM, downstream of Rho1, recruited by the Bin-Amphiphysin-Rvs (BAR)-domain protein, Amphiphysin, around the spermatid heads. Actomyosin activity at the actin-basket gathers the spermatid heads into a compact bundle and resists the invasion of the somatic cell by the intruding spermatids. These observations revealed a new response mechanism of nanoscale bending of the plasma membrane, which generates a novel cell adhesion strategy through active clamping. HighlightsO_LIStretching the plasma membrane around a spermatid head recruits Amphiphysin and Rho1. C_LIO_LIRho1 activation triggers F-actin assembly in situ through Diaphanous and DAAM. C_LIO_LIRho1-Rok activation assembles actomyosin scaffold around the folded plasma membrane. C_LIO_LIContractile actomyosin enables plasma membrane to clamp onto the spermatid head. C_LI Author summarySperm released from the somatic enclosure is essential for male fertility. During differentiation, the somatic cell membrane, associated with dense F-actin scaffold, tightly hold each spermatid head before release. Kapoor et al., showed that the bending and stretching of the plasma membrane trigger the assembly of an actomyosin scaffold around the bent membrane, which clamps the spermatids together preventing the premature release and somatic cell penetration. This finding provides new insight into the molecular networks activated by mechanical bending of the plasma membrane.

cell biology↗

bioRxiv2018

Atypical septate junctions maintain the somatic enclosure around maturing spermatids and prevent premature sperm release in Drosophila testis.

Tight junctions prevent the paracellular flow and maintain cell polarity in an epithelium. These are also essential for maintaining the blood-testis-barrier involved in regulating sperm differentiation. Septate junctions are orthologous to the tight junctions in insects. In Drosophila testis, major septate junction components co-localize at the interface of germline and somatic cells initially and then condense between the two somatic cells in a cyst after germline meiosis. Their localization is extensively remodeled in subsequent stages. We find that characteristic septate junctions are formed between the somatic cyst cells at the elongated spermatid stage. Consistent with the previous reports, knockdown of essential junctional components, Discs-large-1 and Neurexin-IV, in the somatic cyst cells, during the early stages, disrupted sperm differentiation beyond the spermatocyte stage. Somatic knockdown of these proteins during the final stages of spermatid maturation caused premature release of spermatids inside the testes, resulting in partial loss of male fertility. These results indicate the importance of maintaining mechanical integrity of the somatic enclosure during spermatid coiling and release in Drosophila testis. It also highlights the functional similarity with the tight junction proteins during spermatogenesis in mammalian testes.\n\nSummary statementDubey et al., showed that septate junctions stitch the somatic enclosure around maturing spermatids in Drosophila testis. Maintaining the integrity of this junction is essential for proper release of spermatids.

cell biology↗