Drosophila MyoV is essential for rhabdomere development and photoreceptor pigment granule movement

Bingbing Li, Purdue University

Abstract

Sensory neuron terminal differentiation tasks apical secretory transport with delivery of abundant biosynthetic traffic to the growing sensory membrane. We recently showed Drosophila Rab11 is essential for rhodopsin transport in developing photoreceptors and asked here if Myosin-V and the Drosophila Rab11 interacting protein, dRip11, also participate in secretory transport. Reduction of either protein impaired rhodopsin transport, stunting rhabdomere growth and promoting accumulation of cytoplasmic rhodopsin. MyoV-reduced photoreceptors also developed ectopic rhabdomeres inappropriately located in basolateral membrane, indicating a role for MyoV in photoreceptor polarity. Binary yeast two hybrids and in vitro protein-protein interaction predict a ternary complex assembled by independent dRip11 and MyoV binding to Rab11. We propose this complex delivers morphogenic secretory traffic along polarized actin filaments of the subcortical terminal web to the exocytic plasma membrane target, the rhabdomere base. A protein trio conserved across eukaryotes thus mediates normal, in vivo sensory neuron morphogenesis. In response to light, small (100 nm) ommochrome pigment granules in fly photoreceptors migrate to the rhabdomere base, attenuating light propagation along the rhabdomere and downregulating its sensitivity. Pigment granule migration has been shown to depend upon Ca2+ influx, but it is not known which motor is responsible for this movement. Here we show that there is no movement in MyoV hypomorphs and expression of full-length of MyoV in hypomorphs could rescue this phenotype. We also show the Rab-related protein, RabRP1, is important for MyoV localization. We propose that MyoV and RabRP1 form a protein complex to transport pigment granules.

Degree

Ph.D.

Advisors

Ready, Purdue University.

Subject Area

Neurosciences|Genetics|Cellular biology

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