Structure of a PKA RIα Recurrent Acrodysostosis Mutant Explains Defective cAMP-Dependent Activation.

Most disease-related mutations that impair cAMP protein kinase A (PKA) signaling are present within the regulatory (R) PKA RI alpha-subunit (RIα). Although mutations in the PRKAR1A gene are linked to Carney complex (CNC) disease and, more recently, to acrodysostosis-1 (ACRDYS1), the two diseases show contrasting phenotypes. While CNC mutations cause increased PKA activity, ACRDYS1 mutations result in decreased PKA activity and cAMP resistant holoenzymes. Mapping the ACRDYS1 disease mutations reveals their localization to the second of two tandem cAMP-binding (CNB) domains (CNB-B), and here, we characterize a recurrent deletion mutant where the last 14 residues are missing. The crystal structure of a monomeric form of this mutant (RIα92-365) bound to the catalytic (C)-subunit reveals the dysfunctional regions of the RIα subunit. Beyond the missing residues, the entire capping motif is disordered (residues 357-379) and explains the disrupted cAMP binding. Moreover, the effects of the mutation extend far beyond the CNB-B domain and include the active site and N-lobe of the C-subunit, which is in a partially open conformation with the C-tail disordered. A key residue that contributes to this crosstalk, D267, is altered in our structure, and we confirmed its functional importance by mutagenesis. In particular, the D267 interaction with Arg241, a residue shown earlier to be important for allosteric regulation, is disrupted, thereby strengthening the interaction of D267 with the C-subunit residue Arg194 at the R:C interface. We see here how the switch between active (cAMP-bound) and inactive (holoenzyme) conformations is perturbed and how the dynamically controlled crosstalk between the helical domains of the two CNB domains is necessary for the functional regulation of PKA activity.

PKA RIα homodimer structure reveals an intermolecular interface with implications for cooperative cAMP binding and Carney complex disease.

The regulatory (R) subunit is the cAMP receptor of protein kinase A. Following cAMP binding, the inactive PKA holoenzyme complex separates into two active catalytic (C) subunits and a cAMP-bound R dimer. Thus far, only monomeric R structures have been solved, which fell short in explaining differences of cAMP binding for the full-length protein as compared to the truncated R subunits. Here we solved a full-length R-dimer structure that reflects the biologically relevant conformation, and this structure agrees well with small angle X-ray scattering. An isoform-specific interface is revealed between the protomers. This interface acts as an intermolecular sensor for cAMP and explains the cooperative character of cAMP binding to the RIα dimer. Mutagenesis of residues on this interface not only leads to structural and biochemical changes, but is also linked to Carney complex disease.

Comparing factor structure of the Mood Disorder Questionnaire (MDQ): In Italy sexual behavior is euphoric but in Asia mysterious and forbidden.

BACKGROUND: The introduction of screening questionnaires, such as the Mood Disorder Questionnaire (MDQ), has stimulated clinical and epidemiological studies on bipolar disorders. In this work, we studied the item response pattern of the MDQ in the Italian population and compared the results with those of the validation of the MDQ in Asian studies (Chinese and Korean), analyzing similarities and differences among the populations studied. METHODS: The sample was made up of 2278 participants, distributed as follows: 56.6% females, 50.8% living in the north-central Italy, and 33.7% living in rural areas. The factor analysis was run on the matrix of tetrachoric correlations. The psychometric properties of the MDQ were also studied using the Rasch logistic model. RESULTS: The parallel analysis found two significant components. The first includes symptoms referring to acceleration, danger and irritability as risky behaviors, social interaction problems and mental flow. The second includes symptoms referring to self-confidence and energy. With respect to the Korean/Chinese results, the Italian sample, item 11 ("much more sex"), appears related to self-confidence and energy, while in Asia it is connected with items expressing risky behaviors and irritability. LIMITATIONS: Differences in the frequency of comorbid disorders in Asian and Italian populations should be considered. The results should be confirmed and compared with those of other populations. CONCLUSIONS: Cultural differences appear to be associated with a different symptomatic expression of bipolar spectrum disorders. Future research will investigate the role of gene-environment interaction in the genesis of these differences.