April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Autophagy-related secretion of ARMS2
Author Affiliations & Notes
  • Elod Kortvely
    Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
  • Lili Feng
    Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
  • Stefanie M Hauck
    Research Unit for Protein Science, Helmholtz Zentrum München, Munich, Germany
  • Behler Jennifer
    Research Unit for Protein Science, Helmholtz Zentrum München, Munich, Germany
  • Matteo Gorza
    Research Unit for Protein Science, Helmholtz Zentrum München, Munich, Germany
  • Karsten Boldt
    Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
  • Marcel Blindert
    Research Unit for Protein Science, Helmholtz Zentrum München, Munich, Germany
  • Marius Ueffing
    Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
    Research Unit for Protein Science, Helmholtz Zentrum München, Munich, Germany
  • Footnotes
    Commercial Relationships Elod Kortvely, None; Lili Feng, None; Stefanie Hauck, None; Behler Jennifer, None; Matteo Gorza, None; Karsten Boldt, None; Marcel Blindert, None; Marius Ueffing, None
  • Footnotes
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Investigative Ophthalmology & Visual Science April 2014, Vol.55, 1327. doi:
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      Elod Kortvely, Lili Feng, Stefanie M Hauck, Behler Jennifer, Matteo Gorza, Karsten Boldt, Marcel Blindert, Marius Ueffing; Autophagy-related secretion of ARMS2. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1327.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Age-related maculopathy susceptibility 2 (ARMS2) is a small (11 kDa), primate-specific protein implicated in the pathogenesis of age-related macular degeneration (AMD), a leading cause of blindness in elderly. We have previously reported that ARMS2 is actively secreted, although it lacks a typical signal peptide. Here we report that autophagy-related processes are instrumental in conveying ARMS2. Autophagosomes are dynamically formed and serve as a bulk degradation pathway. However, emerging evidence suggests that they are also involved in the biogenesis of transport organelles destined to export a specific group of proteins including ARMS2.

Methods: Several human cell lines were transfected with plasmids coding for ARMS2. Plasmids coding for pro-interleukin (IL)-1β and ARMS2 carrying the desired substitutions were constructed by molecular cloning. The intracellular trafficking of the synthesized protein was monitored by co-staining of well-established markers for different cellular compartments. Digital images of immunostained cells were acquired on a Zeiss Axioscope. The classical secretory pathway was inhibited by using brefeldin A (BFA) in some experiments. ARMS2-positive carriers were isolated for proteomic analysis by native electrophoresis.

Results: Golgi reassembly stacking protein proteins (GRASPs) are the only known markers for unconventional protein secretion. ARMS2-positive vesicle-like structures proved to be positive for this marker. Furthermore, the major proinflammatory cytokine interleukin-1β (IL-1β) is a prototypical example of secretory autophagy. Co-expression of ARMS2 and IL-1β leads to the redistribution of these two proteins into the same vesicle-like structures suggesting a common secretory pathway. On the other hand, co-expression of ARMS2 and HTRA1 (classically secreted protein) or eGFP (non-secreted protein) does not give rise to the colocalization of the two proteins (data not shown), indicating an active cargo selection mechanism. Critical residues within ARMS2 for becoming a client of this transport machinery have also been identified.

Conclusions: Our data suggest that ARMS2 belongs to the group of proteins being secreted by autophagy related mechanisms. Strikingly, all other known proteins hauled by this pathway act pro-inflammatory. Accordingly, ARMS2 might exert its physiological function by regulating immune cells within the eye.

Keywords: 412 age-related macular degeneration • 660 proteins encoded by disease genes • 663 proteomics  
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