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Abstract
Type II Chaperonin Containing TCP-1 (CCT, also known as TCP-1 Ring Complex, TRiC) is a multi-subunit molecular machine thought to assist in the folding of ∼ 10% of newly translated cytosolic proteins in eukaryotes. A number of proteins folded by CCT have been identified in yeast and cultured mammalian cells, however, the function of this chaperonin in vivo has never been addressed. Here we demonstrate that suppressing the CCT activity in mouse photoreceptors by transgenic expression of a dominant-negative mutant of the CCT cofactor, phosducin-like protein (PhLP), results in the malformation of the outer segment, a cellular compartment responsible for light detection, and triggers rapid retinal degeneration. Investigation of the underlying causes by quantitative proteomics identified distinct protein networks, encompassing ∼ 200 proteins, which were significantly affected by the chaperonin deficiency. Notably among those were several essential proteins crucially engaged in structural support and visual signaling of the outer segment such as peripherin 2, Rom1, rhodopsin, transducin, and PDE6. These data for the first time demonstrate that normal CCT function is ultimately required for the morphogenesis and survival of sensory neurons of the retina, and suggest the chaperonin CCT deficiency as a potential, yet unexplored, cause of neurodegenerative diseases.
Highlights
Normal cellular function is hinged upon the ability of the endogenous machinery to properly process newly synthesized proteins, and this is often required for enabling their
These data are in good agreement with previous reports demonstrating that the full-length phosducin-like proteins (PhLP) forms a complex with chaperonin Chaperonin Containing TCP-1 (CCT), and that the ⌬1– 83 deletion of PhLP has no significant effect on this interaction [10, 17]
Ultrastructural examination revealed a unique defect apparently resulting from the failure of the cilium plasma membrane to separate from the rest of the cell into a distinct domain. This observation suggests that suppression of the CCT chaperonin activity affects proteins that mediate cilia membrane transport and morphogenesis. This conclusion is in agreement with the substantial down-regulation of several proteins involved in membrane transport that were identified in our proteomic screen of transgenic retinas
Summary
Normal cellular function is hinged upon the ability of the endogenous machinery to properly process newly synthesized proteins, and this is often required for enabling their. A dataset containing accession numbers of unique proteins identified by mass spectrometry and corresponding expression fold change (linear) was uploaded.
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