Expression analysis of peptidergic enteroendocrine cells in the silkworm Bombyx mori

Insights into midgut cell types and their crucial role in antiviral immunity in the lepidopteran model Bombyx mori

“…EEs discovered around three decades ago ( 64 – 66 ), have two distinct morphological forms, open and closed types ( 67 ), characterized by their peptidergic nature ( 64 ); the former have direct contact with the midgut lumen ( 67 , 68 ), while the latter lacks such interaction as they do not extend through the epithelium ( Figure 1 ) ( 33 , 67 ). The functional application of recent genomic and proteomic approaches provides compelling evidence of the critical role of EEs within the insect midgut play in the physiology and developmental processes of insects ( 56 , 69 , 70 ). The EEs of silkworms were classified into four distinct subtypes according to their spatial distribution.…”

“…The EEs of silkworms were classified into four distinct subtypes according to their spatial distribution. Type I cells were identified across all three midgut regions, while type II, III and IV cells were localized in the anterior, middle, and posterior midgut, respectively ( 56 ). The spatial distribution of EEs across different midgut regions also depends on the specific peptide they produce ( 17 , 71 ).…”

“…The peptides are transformed into active states by cleavage and post-translation modification from protein precursors produced by EEs. In Drosophila , 9 major precursors were identified ( 58 ), whereas in silkworms, 18 distinct protein precursors were identified ( 56 ). In different insects, the peptides produced after cleavage are mainly involved in the regulation of food in the alimentary canal, from reduced ion transport to suppressed gut contractions ( 72 , 73 ).…”