Localization and functional analysis of the insect‐specific RabX4 in the brain of Bombyx mori

Abstract

Rab proteins are small monomeric GTPases/GTP-binding proteins, which form the largest branch of the Ras superfamily. The different Rab GTPases are localized to the cytosolic face of specific intracellular membranes, where they function as regulators of distinct steps in membrane trafficking. RabX4 is an insect-specific Rab protein that has no close homolog in vertebrates. There is little information about insect-specific Rab proteins. RabX4 was expressed in Escherichia coli and subsequently purified. Antibodies against Bombyx mori RabX4 were produced in rabbits for western immunoblotting and immunohistochemistry. Western blotting of neural tissues revealed a single band, at approximately 26 kD. RabX4-like immunohistochemical reactivity was restricted to neurons of the pars intercerebralis and dorsolateral protocerebrum in the brain. Further immunohistochemical analysis revealed that RabX4 colocalized with Rab6 and bombyxin in the corpus allatum, a neuronal organ that secretes neuropeptides synthesized in the brain into the hemolymph. RabX4 expression in the frontal ganglion, part of the insect stomatogastric nervous system that is found in most insect orders, was restricted to two neurons on the outer region and did not colocalize with allatotropin or Rab6. Furthermore, RNA interference of RabX4 decreased bombyxin expression levels in the brain. These findings suggest that RabX4 is involved in the neurosecretion of a secretory organ in Bombyx mori.

Effect of Insulin Receptor on Juvenile Hormone Signal and Fecundity in Spodoptera litura (F.)

“…To analyze the influence of SlInR gene silencing on the expression of Vg protein, a DAB kit was used for Western blot, analyzing its expression. The method was modified according to the protocol previously described [ 36 ]. Briefly, about 20 mg female fat body was homogenized in 250 µL RIPA lysate.…”

Locations of Rab, Allatotropin, Prothoracicotropic hormone and Period in the larval brain, corpus allatum and frontal ganglion of Bombyx mori

“…For example, Rab11 regulates recycling and secretion of membrane proteins between the plasma membrane and endosomes, Rab6 regulates transport in the Golgi apparatus, Rab7 regulates membrane fusion between vesicles and lysosomes and is involved in autophagy, and Rab11 regulates the traffi c and transport of recycling endosomes. Rab14 is located in Golgi/TGN Antiserum production Antisera against B. mori Rab1,3,6,7,11,14,21, X4, and PTTH, PER and AT were obtained as previously described (Uno et al, 2010(Uno et al, , 2013(Uno et al, , 2016(Uno et al, , 2017(Uno et al, , 2021. The specifi city of the antibodies is shown in Table 1.…”

Immune function of a Rab‐related protein by modulating the JAK‐STAT signaling pathway in the silkworm, Bombyx mori

“…Dysfunction of Rab proteins can lead to Choroideremia, Carpenter syndrome, and other human diseases (Bhuin & Roy, 2014). Rab family members in invertebrates were reported to be involved in the development of neurons and the conduction of synapses in Bombyx mori, C. elegans, and D. melanogaster (Chan et al, 2011;Mahoney et al, 2006;Uno et al, 2017). Knockdown of invertebrate Rab can induce apoptosis, and Rab7 plays an important role in the phagocytosis of apoptotic cells of C. elegans (Guo, Hu, Zhang, Jiang, & Wang, 2010).…”

“…It is also a lepidopteran model organism for genetic and immunology research (Liu, Ling, & Wu, 2009;Rao et al, 2016;Wang et al, 2017). In silkworms, the Rab protein mainly functions in the development of neurons (Uno et al, 2010(Uno et al, , 2013(Uno et al, , 2014(Uno et al, , 2016(Uno et al, , 2017. However, there is no report on the role of Rab in the innate immunity of the silkworm.…”