Loss of PKA regulatory subunit 1α aggravates cardiomyocyte necrosis and myocardial ischemia/reperfusion injury.

Reperfusion therapy, the standard treatment for acute myocardial infarction, can trigger necrotic death of cardiomyocytes and provoke ischemia/reperfusion (I/R) injury. However, signaling pathways that regulate cardiomyocyte necrosis remain largely unknown. Our recent genome-wide RNAi screen has identified a potential necrosis suppressor gene PRKAR1A, which encodes PKA regulatory subunit 1α (R1α). R1α is primarily known for regulating PKA activity by sequestering PKA catalytic subunits in the absence of cAMP. Here, we showed that depletion of R1α augmented cardiomyocyte necrosis in vitro and in vivo, resulting in exaggerated myocardial I/R injury and contractile dysfunction. Mechanistically, R1α loss downregulated the Nrf2 antioxidant transcription factor and aggravated oxidative stress following I/R. Degradation of the endogenous Nrf2 inhibitor Keap1 through p62-dependent selective autophagy was blocked by R1α depletion. Phosphorylation of p62 at Ser349 by mammalian target of rapamycin complex 1 (mTORC1), a critical step in p62-Keap1 interaction, was induced by I/R, but diminished by R1α loss. Activation of PKA by forskolin or isoproterenol almost completely abolished hydrogen-peroxide-induced p62 phosphorylation. In conclusion, R1α loss induces unrestrained PKA activation and impairs the mTORC1-p62-Keap1-Nrf2 antioxidant defense system, leading to aggravated oxidative stress, necrosis, and myocardial I/R injury. Our findings uncover a novel role of PKA in oxidative stress and necrosis, which may be exploited to develop new cardioprotective therapies.

MANAGEMENT OF ENDOCRINE DISEASE: Carney complex: clinical and genetic update 20 years after the identification of the CNC1 (PRKAR1A) gene.

Described for the first time in 1985, Carney complex (CNC) is a rare dominantly inherited multiple neoplasia syndrome with almost full penetrance and characterized by both endocrine - primary pigmented nodular adrenocortical disease with Cushing's syndrome, acromegaly and thyroid tumors - and non-endocrine manifestations such as cardiac, cutaneous and mucosal myxomas, pigmented cutaneous lesions, psammomatous melanotic schwannoma, osteochondromyxoma and a wide range of other tumours with potential malignancy. The pathophysiology of CNC is a model of dysregulation of the cAMP/PKA signalling in human diseases. As described 20 years ago, inactivating heterozygous mutations of PRKAR1A formerly known as CNC1, encoding the regulatory subunit 1α of protein kinase A, are identified in more than 70% of the index cases, while inactivating mutations of genes encoding phosphodiesterases are found in rare and particular forms of the complex. There is at present no medical specific treatment for CNC, every confirmed or suspected CNC patient should be managed by a multi-disciplinary team according to each manifestation of the disease and offered a long-term follow-up and genetic counselling. The better knowledge that we have now of this fascinating rare disease and its genetics will help to improve patients outcome.

Embolic stroke, left atrial myxoma and gigantism in a patient with Carney complex with additional features suggestive of Marfan syndrome.

A 16-year-old boy presented to the emergency department with a sudden weakness on the right side of the body and was diagnosed as having embolic stroke. Later on, the patient was diagnosed as having Carney complex (CNC). The neurological complication might be caused by left atrial myxoma as a feature of CNC. Surprisingly, the patient showed some additional features such as positive wrist and thumb signs, pectus carinatum deformity and plain flat feet, suggestive of Marfan syndrome. This case demonstrated that both of these syndromes might coexist in the same patient, suggesting that proper diagnostic and management were key factors that affected prognosis. He showed an improved condition after he had received medical treatments, undergone tumour excision and physiotherapy. Further evaluation was needed to improve patient outcomes.

Carney complex: an update.

Carney complex (CNC) is a rare autosomal dominant syndrome, characterized by pigmented lesions of the skin and mucosa, cardiac, cutaneous and other myxomas and multiple endocrine tumors. The disease is caused by inactivating mutations or large deletions of the PRKAR1A gene located at 17q22-24 coding for the regulatory subunit type I alpha of protein kinase A (PKA) gene. Most recently, components of the complex have been associated with defects of other PKA subunits, such as the catalytic subunits PRKACA (adrenal hyperplasia) and PRKACB (pigmented spots, myxomas, pituitary adenomas). In this report, we review CNC, its clinical features, diagnosis, treatment and molecular etiology, including PRKAR1A mutations and the newest on PRKACA and PRKACB defects especially as they pertain to adrenal tumors and Cushing's syndrome.

Familial pituitary tumors.

Pituitary adenomas are benign intracranial neoplasms that present a major clinical concern due to hormone overproduction and/or tumor mass effects. The majority of pituitary adenomas occur sporadically; however, familial cases are increasingly being recognized, such as multiple endocrine neoplasia type 1 (MEN1), Carney complex (CNC), and familial isolated pituitary adenoma (FIPA). Familial pituitary tumors appear to differ from their sporadic counterparts both in their genetic basis and in clinical characteristics. Evidence suggests that, especially in MEN1 and FIPA, tumors are more aggressive and affect patients at a younger age, therefore justifying the importance of early diagnosis, while in Carney complex pituitary hyperplasia is common. The genetic alterations responsible for the formation of familial pituitary syndromes include the MEN1 gene, responsible for about 80% of MEN1 cases, the regulatory subunit of the protein kinase A, PRKAR1A, responsible for about 70% of Carney complex cases, and AIP, the gene coding the aryl hydrocarbon receptor interacting protein, responsible for about 20% of FIPA cases. Rarely other genes have also been found responsible for familial pituitary adenoma cases. McCune-Albright syndrome (MAS) also has a genetic origin due to mosaic mutations in the G protein-coupled α subunit coded by the GNAS1 gene. In this chapter, we summarize the genetic and clinical characteristics of these familial pituitary syndromes and MAS.

Recurrent left atrial myxomas in Carney complex: a genetic cause of multiple strokes that can be prevented.

BACKGROUND: Intracardiac myxomas in Carney complex are significant causes of cardiovascular morbidity and mortality through embolic stroke and heart failure. The genetic, clinical, and laboratory characteristics of Carney complex-related strokes from atrial myxomas have not been described. The regulatory subunit (R1A) of the protein kinase gene (PRKAR1A) is mutated in >60% of patients with Carney complex. METHODS: We studied patients with strokes and cardiac myxomas that were hospitalized in our institution and elsewhere; a total of 7 patients with 16 recurrent atrial myxomas and >14 episodes of strokes were identified. RESULTS: Neurologic deficits were reported; in 1 patient, an aneurysm developed at the site of a previous stroke. All patients were females, were also diagnosed with Cushing syndrome, and all had additional tumors or other Carney complex manifestations. Other than gender, although there was a trend for patients being overweight and hypertensive, no other risk factors were identified. A total of 5 patients (71%) had a PRKAR1A mutation; all mutations (c418_419delCA, c.340delG/p.Val113fsX15, c.353_365del13/p.Ile118fsX6, c.491_492delTG/p.Val164fsX4, and c.177+1G>A) were located in exons 3 to 5 and introns 2 to 3, and all led to a non-sense PRKAR1A mRNA. CONCLUSIONS: Female patients with Carney complex appear to be at a high risk for recurrent atrial myxomas that lead to multiple strokes. Early identification of a female patient with Carney complex is of paramount importance for the early diagnosis of atrial myxomas and the prevention of strokes.