RESUMEN
Hereditary spastic paraplegias (HSPs) are a diverse group of neurodegenerative diseases that are characterized by axonopathy of the corticospinal motor neurons. A mutation in the gene encoding for Tectonin ß-propeller containing protein 2 (TECPR2) causes HSP that is complicated by neurological symptoms. While TECPR2 is a human ATG8 binding protein and positive regulator of autophagy, the exact function of TECPR2 is unknown. Here, we show that TECPR2 associates with several trafficking components, among them the COPII coat protein SEC24D. TECPR2 is required for stabilization of SEC24D protein levels, maintenance of functional ER exit sites (ERES), and efficient ER export in a manner dependent on binding to lipidated LC3C. TECPR2-deficient HSP patient cells display alterations in SEC24D abundance and ER export efficiency. Additionally, TECPR2 and LC3C are required for autophagosome formation, possibly through maintaining functional ERES. Collectively, these results reveal that TECPR2 functions as molecular scaffold linking early secretion pathway and autophagy.
Asunto(s)
Autofagia , Proteínas Portadoras/metabolismo , Retículo Endoplásmico/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Transporte de Proteínas , Paraplejía Espástica Hereditaria/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis , Proteínas Portadoras/genética , Células HeLa , Humanos , Mutación , Proteínas del Tejido Nervioso/genética , Paraplejía Espástica Hereditaria/metabolismo , Proteínas de Transporte Vesicular/metabolismoRESUMEN
We currently lack a broader mechanistic understanding of the integration of the early secretory pathway with other homeostatic processes such as cell growth. Here, we explore the possibility that Sec16A, a major constituent of endoplasmic reticulum exit sites (ERES), acts as an integrator of growth factor signaling. Surprisingly, we find that Sec16A is a short-lived protein that is regulated by growth factors in a manner dependent on Egr family transcription factors. We hypothesize that Sec16A acts as a central node in a coherent feed-forward loop that detects persistent growth factor stimuli to increase ERES number. Consistent with this notion, Sec16A is also regulated by short-term growth factor treatment that leads to increased turnover of Sec16A at ERES. Finally, we demonstrate that Sec16A depletion reduces proliferation, whereas its overexpression increases proliferation. Together with our finding that growth factors regulate Sec16A levels and its dynamics on ERES, we propose that this protein acts as an integrator linking growth factor signaling and secretion. This provides a mechanistic basis for the previously proposed link between secretion and proliferation.
Asunto(s)
Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Proliferación Celular/fisiología , Retículo Endoplásmico/metabolismo , Vías Secretoras/fisiología , Proteínas de Transporte Vesicular/metabolismo , Línea Celular , Proliferación Celular/genética , Proteína 1 de la Respuesta de Crecimiento Precoz/genética , Proteína 3 de la Respuesta de Crecimiento Precoz/genética , Factores de Transcripción de la Respuesta de Crecimiento Precoz/metabolismo , Aparato de Golgi/metabolismo , Células HeLa , Células Hep G2 , Humanos , Proteínas de Unión al GTP Monoméricas/genética , Nucleósido Difosfato Quinasas NM23/genética , Nucleósido-Difosfato Quinasa/genética , Fosfotransferasas (Aceptor de Grupo Alcohol)/genética , Transducción de Señal , Proteínas de Transporte Vesicular/genéticaRESUMEN
The components that control trafficking between organelles of the secretory pathway as well as their architecture were uncovered to a reasonable extent in the past decades. However, only recently did we begin to explore the regulation of the secretory pathway by cellular signaling. In the current review, we focus on trafficking between the endoplasmic reticulum and the Golgi apparatus. We highlight recent advances that have been made toward a better understanding of how the secretory pathway is regulated by signaling and discuss how this knowledge is important to obtain an integrative view of secretion in the context of other homeostatic processes such as growth and proliferation.