{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,3]],"date-time":"2026-04-03T18:28:58Z","timestamp":1775240938046,"version":"3.50.1"},"reference-count":43,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2014,8,29]],"date-time":"2014-08-29T00:00:00Z","timestamp":1409270400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biomolecules"],"abstract":"<jats:p>Proteasomes regulate many essential cellular processes by degrading intracellular proteins. While aging is known to be associated with dysfunction of the proteasome,  there are few reports detailing activity and function of proteasomes in the early stages of life. To elucidate the function and development of mammalian proteasomes, 26S proteasomes were affinity-purified from rat intestine, spleen and liver. The developmental expression  of core, regulatory and immunoproteasome subunits was analyzed by immunoblotting and reverse-transcriptase PCR of mRNA subunits, and proteasome catalytic function was determined by fluorogenic enzymatic assays. The expression of core (\u03b22, \u03b25, \u03b17 and \u03b21) and regulatory (Rpt5) subunits was found to be present at low levels at birth and increased over time particularly at weaning. In contrast, while gradual developmental progression of proteasome structure was also seen with the immunoproteasome subunits (\u03b21i, \u03b25i, and \u03b22i), these were not present at birth. Our studies demonstrate a developmental pattern to  26S proteasome activity and subunit expression, with low levels of core proteasome components and absence of immunoproteasomes at birth followed by increases at later developmental stages. This correlates with findings from other studies of a developmental hyporesponsiveness of the adaptive immune system to allow establishment of microbial colonization immediately after birth.<\/jats:p>","DOI":"10.3390\/biom4030812","type":"journal-article","created":{"date-parts":[[2014,8,29]],"date-time":"2014-08-29T10:37:19Z","timestamp":1409308639000},"page":"812-826","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Differential Expression of 26S Proteasome Subunits and Functional Activity during Neonatal Development"],"prefix":"10.3390","volume":"4","author":[{"given":"Erika","family":"Claud","sequence":"first","affiliation":[{"name":"Departments of Pediatrics and Medicine, University of Chicago, Chicago, IL 60611, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Julie","family":"McDonald","sequence":"additional","affiliation":[{"name":"Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University,  Kingston, ON K7L 2V7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shu-Mei","family":"He","sequence":"additional","affiliation":[{"name":"Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University,  Kingston, ON K7L 2V7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yueyue","family":"Yu","sequence":"additional","affiliation":[{"name":"Departments of Pediatrics and Medicine, University of Chicago, Chicago, IL 60611, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lily","family":"Duong","sequence":"additional","affiliation":[{"name":"Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University,  Kingston, ON K7L 2V7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jun","family":"Sun","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, Rush University, Chicago, IL 60612, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Elaine","family":"Petrof","sequence":"additional","affiliation":[{"name":"Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University,  Kingston, ON K7L 2V7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2014,8,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1203\/01.PDR.0000050141.73528.AD","article-title":"Modulation of human intestinal epithelial cell IL-8 secretion by human milk factors","volume":"53","author":"Claud","year":"2003","journal-title":"Pediatr. 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