Molecular Cell paper reported that aPKC prevents degradation of SRC-3 through estrogen receptor-selective event.

Baylor College of Medicine researchers found a new mechanism that regulates a prominent cancer-associated protein. It is well established that steroid receptor coactivator-3 (SRC-3/AIB1), which plays key roles in cell growth, reproduction, metabolism, and cytokine signaling, is overexpressed in many cancers and is a major player in tumorigenesis and cancer progression.

“Recently, it was shown that phosphorylation of SRC-3 by specific kinases is associated with increased degradation of SRC-3. However, kinases that stabilize SRC-3 in cancer cells have not yet been reported,” explains lead author, Bert O’Malley, M.D., professor and chairman of the department of molecular and cellular biology.

Dr. O’Malley and colleagues examined the interaction between atypical protein kinase C (aPKC), which is overexpressed in many cancers, and SRC-3. They found that aPKC induced phosphorylation of a particular region of SRC-3 thus stabilizing cellular protein levels. Specifically, phosphorylation of C-terminal residues induced a conformational change that made SRC-3 more resistant to degradation by the core proteasome.

aPKC’s effect required estrogen and estrogen receptor and was not supported by other steroid receptors, suggesting that aPKC-mediated SRC-3 stabilization is a receptor-selective event, according to the scientists.

The research will be published in the February 29 issue of Molecular Cell.

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