RESUMEN
Autophagy plays an essential role in intracellular degradation and maintenance of cellular homeostasis in all cells, including neurons. Although a recent study reported a copy number variation of Ulk2, a gene essential for initiating autophagy, associated with a case of schizophrenia (SZ), it remains to be studied whether Ulk2 dysfunction could underlie the pathophysiology of the disease. Here we show that Ulk2 heterozygous (Ulk2+/-) mice have upregulated expression of sequestosome-1/p62, an autophagy-associated stress response protein, predominantly in pyramidal neurons of the prefrontal cortex (PFC), and exhibit behavioral deficits associated with the PFC functions, including attenuated sensorimotor gating and impaired cognition. Ulk2+/- neurons showed imbalanced excitatory-inhibitory neurotransmission, due in part to selective down-modulation of gamma-aminobutyric acid (GABA)A receptor surface expression in pyramidal neurons. Genetically reducing p62 gene dosage or suppressing p62 protein levels with an autophagy-inducing agent restored the GABAA receptor surface expression and rescued the behavioral deficits in Ulk2+/- mice. Moreover, expressing a short peptide that specifically interferes with the interaction of p62 and GABAA receptor-associated protein, a protein that regulates endocytic trafficking of GABAA receptors, also restored the GABAA receptor surface expression and rescued the behavioral deficits in Ulk2+/- mice. Thus, the current study reveals a novel mechanism linking deregulated autophagy to functional disturbances of the nervous system relevant to SZ, through regulation of GABAA receptor surface presentation in pyramidal neurons.
Asunto(s)
Autofagia/genética , Proteínas Serina-Treonina Quinasas/genética , Esquizofrenia/genética , Proteína Sequestosoma-1/genética , Animales , Variaciones en el Número de Copia de ADN/genética , Regulación de la Expresión Génica/genética , Humanos , Ratones , Péptidos/genética , Corteza Prefrontal/metabolismo , Corteza Prefrontal/patología , Transporte de Proteínas/genética , Células Piramidales/metabolismo , Células Piramidales/patología , Receptores de GABA-A/genética , Esquizofrenia/fisiopatología , Transmisión Sináptica/genéticaRESUMEN
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that, while prevalent, has a stagnant track record for advances in treatment. The limited availability of animal models with appropriate face and predictive validities has hampered progress in developing novel neurobiological hypotheses and testing new therapeutic options for this condition. Here, we report that mice deficient in Fez1, a gene specifically expressed in the nervous system with documented functions in neurodevelopment, show hyperactivity and impulsivity phenotypes, which are ameliorated by administering methylphenidate (MPH) or guanfacine (GFC), two pharmacological agents used for ADHD treatment. Fez1-knockout (KO) mice show reduced expression of tyrosine hydroxylase in the midbrain and the brain stem and have reduced levels of dopamine, norepinephrine, or their metabolites in both the nucleus accumbens and the prefrontal cortex. These neurochemical changes in Fez1-KO mice were normalized by MPH or GFC. We propose that Fez1-KO mice can be used as a model to evaluate the role of altered neurodevelopment in the manifestation of ADHD-like behavioral phenotypes, as well as to investigate the neurobiological mechanisms of existing and new pharmacotherapeutic agents for ADHD.
RESUMEN
Alcoholism is a psychiatric condition that develops through neuroadaptations in response to neuronal stresses caused by chronic ethanol intake. Neurons can adapt to ethanol-induced metabolic changes by activating cellular protective mechanisms, including autophagy. Here we show that expression of Ulk1, a gene critical to the regulation of autophagy, was affected in the prefrontal cortex (PFC) of mice following chronic intermittent ethanol (CIE) exposure. Consequently, overall levels of Ulk1 activity in the PFC were downregulated, leading to accumulation of p62, a protein that serves as a target for autophagic degradation. In addition, Ulk1-null mice demonstrated decline in the exploratory activity, deficits in the ability to recognize novel objects following CIE exposure, and reduced rate of voluntary ethanol drinking. The data suggest the neuroprotective role for Ulk1-mediated autophagy in the suppression of neuropsychiatric manifestation during ethanol exposure.