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bioRxiv · 10.1101/2024.04.05.588361

Ca2+ binding to Esyt is required to modulate membrane contact site density in Drosophila photoreceptors

Nath, V. R.·Krishnan, H.·Mishra, S.·PADINJAT, R.
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Abstract

Membrane Contact Sites (MCS) between the plasma membrane (PM) and endoplasmic reticulum (ER) have been shown to regulate Ca2+ influx into animal cells. However, the mechanisms by which cells modulate ER-PM MCS density is not understood and the role of Ca2+, if any, in regulating this process is not known. We report that in Drosophila photoreceptors, MCS density is dependent on the activity of the Ca2+ permeable channels-TRP and TRPL. This regulation of MCS density by Ca2+ is mediated by extended synaptotagmin (dEsyt), a protein localised to ER-PM MCS in photoreceptors and previously shown to regulate MCS density. We find that the Ca2+ binding activity of dEsyt is required for its functional activity in vivo. dEsytCaBM, a Ca2+ non-binding mutant of dEsyt is unable to modulate MCS structure in a manner equivalent to its wild type counterpart. Further, when reconstituted in dEsyt null photoreceptors, in contrast to wild type dEsyt, dEsytCaBM is unable to rescue ER-PM MCS density and other key phenotypes. Finally, when expressed in wild type photoreceptors, dEsytCaBM phenocopies loss of dEsyt function. Taken together, our data supports a role for the Ca2+ binding activity of dEsyt in regulating the ER-PM MCS density in photoreceptors thus tuning signal transduction in response to Ca2+ influx triggered by ambient illumination. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/588361v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@f8faacorg.highwire.dtl.DTLVardef@114009org.highwire.dtl.DTLVardef@8337f0org.highwire.dtl.DTLVardef@cd7c2f_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Nath, V. R., Krishnan, H., Mishra, S., PADINJAT, R.. 2024-04-06. Ca2+ binding to Esyt is required to modulate membrane contact site density in Drosophila photoreceptors. https://doi.org/10.1101/2024.04.05.588361

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