Protein kinase C (PKC) is a signal transduction protein that has been proposed to mediate rapid responses to steroid hormones. Previously, we have shown aldosterone directly activates PKCalpha whereas 17beta-estradiol activates PKCalpha and PKCdelta; however, neither the binding to PKCs nor the mechanism of action has been established. To determine the domains of PKCalpha and PKCdelta involved in binding of aldosterone and 17beta-estradiol, glutathione S-transferase fusion recombinant PKCalpha and PKCdelta mutants were used to perform in vitro binding assays with [(3)H]aldosterone and [(3)H]17beta-estradiol. 17beta-Estradiol bound both PKCalpha and PKCdelta but failed to bind PKC mutants lacking a C2 domain. Similarly, aldosterone bound only PKCalpha and mutants containing C2 domains. Thus, the C2 domain is critical for binding of these hormones. Binding affinities for aldosterone and 17beta-estradiol were between 0.5-1.0 nM. Aldosterone and 17beta-estradiol competed for binding to PKCalpha, suggesting they share the same binding site. Phorbol 12,13-dybutyrate did not compete with hormone binding; furthermore, they have an additive effect on PKC activity. EC(50) for activation of PKCalpha and PKCdelta by aldosterone and 17beta-estradiol was approximately 0.5 nM. Immunoblot analysis using a phospho-PKC antibody revealed that upon binding, PKCalpha and PKCdelta undergo autophosphorylation with an EC(50) in the 0.5-1.0 nm range. 17beta-Estradiol activated PKCalpha and PKCdelta in estrogen receptor-positive and -negative breast cancer cells (MCF-7 and HCC-38, respectively), suggesting estrogen receptor expression is not required for 17beta-estradiol-induced PKC activation. The present results provide first evidence for direct binding and activation of PKCalpha and PKCdelta by steroid hormones and the molecular mechanisms involved.

BACKGROUND:Our prior research has demonstrated that increasing the number of trauma centers (TCs) in a state does not reliably improve state-level injury-related mortality. We hypothesized that many new TCs would serve populations already served by existing TCs, rather than in areas without ready TC access. We also hypothesized that new TCs would also be less likely to serve economically disadvantaged populations. METHODS:All state-designated adult TCs registered with the American Trauma Society in 2014 and 2019 were mapped using ArcGIS Pro (ESRI Inc., Redlands, CA). Trauma centers were grouped as Level 1 or 2 (Lev12) or Level 3, 4 or 5 (Lev345). We also obtained census tract-level data (73,666 tracts), including population counts and percentage of population below the federal poverty threshold. Thirty-minute drive-time areas were created around each TC. Census tracts were considered "served" if their geographic centers were located within a 30-minute drive-time area to any TC. Data were analyzed at the census tract level. RESULTS:A total of 2,140 TCs were identified in 2019, with 256 new TCs and 151 TC closures. Eighty-two percent of new TCs were Levels 3 to 5. Nationwide, coverage increased from 75.3% of tracts served in 2014 to 78.1% in 2019, representing an increased coverage from 76.0% to 79.4% of the population. New TC served 17,532 tracts, of which 87.3% were already served. New Lev12 TCs served 9,100 tracts, of which 91.2% were already served; new Lev345 TCs served 15,728 tracts, of which 85.9% were already served. Of 2,204 newly served tracts, those served by Lev345 TCs had higher mean percentage poverty compared with those served by Lev12 TCs (15.7% vs. 13.2% poverty, p < 0.05). DISCUSSION:Overall, access to trauma care has been improving in the United States. However, the majority of new TCs opened in locations with preexisting access to trauma care. Nationwide, Levels 3, 4, and 5 TCs have been responsible for expanding access to underserved populations.