{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T21:45:58Z","timestamp":1790718358735,"version":"4.1.0"},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1998,6,15]]},"abstract":"<jats:p>Small heat-shock proteins (sHSPs) are widely expressed 25\u201328\u00a0kDa proteins whose functions are dynamically regulated by phosphorylation. While recent efforts have clearly delineated a stress-responsive p38 mitogen-activated protein-kinase (MAPK)-dependent kinase pathway culminating in activation of the heat-shock (HSP)-kinases, mitogen-activated protein-kinase-activated protein kinase-2 and -3, not all sHSP phosphorylation events can be explained by the p38 MAPK-dependent pathway. The contribution of protein kinase C (PKC) to sHSP phosphorylation was suggested by early studies but later questioned on the basis of the reported poor ability of purified PKC to phosphorylate sHSP in vitro. The current study re-evaluates the role of PKC in sHSP phosphorylation in the light of the isoform complexity of the PKC family. We evaluated the sHSP phosphorylation status in rat corpora lutea obtained from two stages of pregnancy, mid-pregnancy and late-pregnancy, which express different levels of the novel PKC isoform, PKC-\u03b4. Two-dimensional Western blot analysis showed that HSP-27 was more highly phosphorylated in vivo in corpora lutea of late pregnancy, corresponding to the developmental stage in which PKC-\u03b4 is abundant and active. Late-pregnant luteal extracts contained a lipid-sensitive HSP-kinase activity which exactly co-purified with PKC-\u03b4 using hydroxyapatite and S-Sepharose column chromatography. To determine whether there might be preferential phosphorylation of sHSP by a particular PKC isoform, purified recombinant PKC isoforms corresponding to those PKC isoforms detected in rat corpora lutea were evaluated for HSP-kinase activity in vitro. Recombinant PKC-\u03b4 effectively catalysed the phosphorylation of sHSP in vitro, and PKC-\u03b1 was 30\u201350% as effective as an HSP-kinase; other PKCs tested (\u03b21, \u03b22, \u03b5 and \u03b6) were poor HSP-kinases. These results show that select PKC family members can function as direct HSP-kinases in vitro. Moreover, the observation of enhanced luteal HSP-27 phosphorylation in vivo, in late pregnancy, when PKC-\u03b4 is abundant and active, suggests that select PKC family members contribute to sHSP phosphorylation events in vivo.<\/jats:p>","DOI":"10.1042\/bj3320703","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T22:02:02Z","timestamp":1439244122000},"page":"703-712","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":104,"title":["Heat-shock protein-25\/27 phosphorylation by the \u03b4 isoform of protein kinase C"],"prefix":"10.1042","volume":"332","author":[{"given":"Evelyn T.","family":"MAIZELS","sequence":"first","affiliation":[{"name":"Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, U.S.A."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carl A.","family":"PETERS","sequence":"additional","affiliation":[{"name":"Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, U.S.A."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"KLINE","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, Molecular and Cell Biology, Northwestern University, Evanston, IL 60208, U.S.A."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"suffix":"Jr.","given":"Richard E.","family":"CUTLER","sequence":"additional","affiliation":[{"name":"Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, U.S.A."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Malathy","family":"SHANMUGAM","sequence":"additional","affiliation":[{"name":"Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, U.S.A."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mary","family":"HUNZICKER-DUNN","sequence":"additional","affiliation":[{"name":"Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, U.S.A."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/332\/3\/703\/630737\/bj3320703.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/332\/3\/703\/630737\/bj3320703.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,24]],"date-time":"2021-11-24T00:28:10Z","timestamp":1637713690000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/332\/3\/703\/33656\/Heat-shock-protein-25-27-phosphorylation-by-the"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1998,6,15]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1998,6,15]]}},"URL":"https:\/\/doi.org\/10.1042\/bj3320703","relation":{},"ISSN":["0264-6021","1470-8728"],"issn-type":[{"value":"0264-6021","type":"print"},{"value":"1470-8728","type":"electronic"}],"subject":[],"published":{"date-parts":[[1998,6,15]]}}}