Solution Structure and Expression Profile of an Insect Cytokine: Manduca sexta Stress Response Peptide-2

Abstract

Manduca sexta stress response peptide-2 (SRP2) is predicted to be a 25-residue peptide (FGVKDGKCPSGRVRRLGICVPDDDY), which may function as an insect cytokine to regulate immune responses. Produced as an inactive precursor, endogenous proSRP2 is probably converted to active SRP2 by limited proteolysis in response to invading pathogens, along with prophenoloxidase and pro-Spätzle activation. In addition to immunity, SRP2 may control head morphogenesis or other developmental processes in the lepidopteran insect. We have examined the profiles of SRP2 gene expression in terms of immune induction capacity, tissue specificity, and developmental changes. To gain insights into its functions, we chemically synthesized SRP2, injected the peptide solution into naïve larvae, and detected significant up-regulation of several antimicrobial peptide genes. We determined the 3D molecular structure in solution of SRP2 by two-dimensional 1H-1H NMR spectroscopy. SRP2 has an ordered structure, which is composed of two short ß-strands at regions R12 - R15 and I18 - V20, one type-I’ ß-turn at region R15 - I18, and a half turn at region C8 - S10 in its well-defined core stabilized by a covalent disulfide bond between C8 and C19. The secondary and tertiary structures are further stabilized by hydrogen bonds. Possible relationships between the structure and function are also discussed.

The Orphan Cytokine Receptor CRLF3 Emerged With the Origin of the Nervous System and Is a Neuroprotective Erythropoietin Receptor in Locusts

“…In contrast to vertebrates, only few cytokines or cytokine-like peptides have been identified in insects (Duressa et al, 2015; Schrag et al, 2017; Matsumura et al, 2018). Expression of CRLF3 by locust hemocytes and brain cells may indicate multiple production sites of its endogenous ligand, since blood-brain-barriers restrict the exchange of ions and soluble molecules (reviewed in DeSalvo et al, 2011).…”

Ecdysis triggering hormone peptide in the African malaria mosquito Anopheles gambiae: The peptide structure for receptor activation

“…Before processing, the t2 dimension of DQF‐COSY data sets was zero‐filled to 4k and t1 dimension to 2K. Side‐chain proton resonances were assigned as previously discussed (Schrag et al ., 2017 ) by overlaying cross peaks in the TOCSY spectra with those in the NOESY spectra acquired under similar conditions. NOE cross peaks were classified as strong, medium, or weak intensity based on the number of contour lines observed.…”