Intestinal hydrolase transcriptional and proteomic responses during rapid diet adjustment in nestling house sparrows (Passer domesticus)

KARASOV WH; ANTONIO BRUN; MAGALLANES, MELISA; ROTT, KATHERINE H.; CHRISTINA ROSS; CAVIEDES-VIDAL E

La Habana

Congreso; PHYSIOLOGY WITHOUT BORDERS II Panamerican; 2019

American Physiological Society

Many bird species increase intestinal hydrolase activity when exposed to an increase of the specific substrate in the diet. To increase understanding of the underlying mechanism(s), we studied nestling house sparrows (HOSP; Passer domesticus) switched between high protein diet (63% protein/5% starch) and high starch diet (30% protein/38% starch). In nature, the nestlings undergo a natural switch from high protein insects to starch-containing seed diet during development. In HOSP, like the majority of passerines, both maltasic and sucrasic activity of the small intestine arise from a single gene, which we call AAG (?ancestral? alpha-glucosidase), that is homologous for the one that codes for the sucrase-isomaltase of mammals. We measured activities of AAG and peptidase (APN; amino peptidase-N) in whole intestinal homogenates and in brush border membrane (bbm) isolates, and their respective mRNA by qPCR in intestinal tissue (Gatica-Sosa, C. et al. (2016) J. Anim. Physiol. & Anim. Nutr. 100 236?242; follows MIQE guidelines). In bbm isolates, proteins were solubilized, digested and chromatographically separated. Peptides were analyzed by nano LC-MS/MS. MS/MS data were used to search against Uniprot and RefSeq databases . Hydrolases (i.e. their spectra) represented approximately 3% of the total protein (total spectra) detected. Both intestinal AAG and peptidase (APN; amino peptidase-N) activity, and their respective mRNA, were induced by their respective substrates within 24 h of a diet shift - consistent with the hypothesis that altered gene expression occurs in mature enterocytes on intestinal villi. Dietary induction of both maltasic and sucrasic activity followed the same time course, which matched the time course for expression of AAG mRNA ? all as expected for a 1-enzyme system under transcriptional control. For AAG, evidence indicated that induction of transcription began >18 h after diet switch, and incorporation of new protein and activity in the apical brush border membrane occurred in