The trafficking of bacterial type rhodopsins into the Chlamydomonas eyespot and flagella is IFT mediated.

Mayanka Awasthi,Suneel Kateriya,Peeyush Ranjan,Sindhu Kandoth Veetil,Komal Sharma

doi:10.1038/srep34646

Mayanka Awasthi, Suneel Kateriya + Show 3 more

Open Access

https://doi.org/10.1038/srep34646

Copy DOI

Abstract

The bacterial type rhodopsins are present in all the three domains of life. In contrast to the animal type rhodopsin that performs mainly sensory functions in higher eukaryotes, the bacterial type rhodopsin could function as ion channel, pumps and as sensory proteins. The functioning of rhodopsin in higher eukaryotes requires the transport of rhodopsin from its site of synthesis to the ciliated outer segment of the photoreceptive cells. However, the trafficking of bacterial type rhodopsin from its site of synthesis to the position of action is not characterized. Here we present the first report for the existence of an IFT-interactome mediated trafficking of the bacterial type rhodopsins into eyespot and flagella of the Chlamydomonas. We show that there is a light-dependent, dynamic localization of rhodopsins between flagella and eyespot of Chlamydomonas. The involvement of IFT components in the rhodopsin trafficking was elucidated by the use of conditional IFT mutants. We found that rhodopsin can be co-immunoprecipitated with the components of IFT machinery and with other protein components required for the IFT-cargo complex formation. These findings show that light-regulated localization of rhodopsin is not restricted to animals thereby suggesting that rhodopsin trafficking is an IFT dependent ancient process.

Highlights

Rhodopsin is the key photoreceptor that mediates the photobehavioural responses in different organisms[1,2,3]
This study leads to the identification of a novel rhodopsin present in Chlamydomonas reinhardtii, which we named as Chlamyopsin 8 or Cop[8]
Cop[8] is a multidomain rhodopsin where N-terminal of rhodopsin is flanked with potassium channel and cyclic nucleotide-monophosphate binding domain, and C-terminal harbor other modular domains like, Histidine kinase (Hk) and response regulator and cyclase domains (Supplementary Fig. 1e)

Summary

Introduction

Rhodopsin is the key photoreceptor that mediates the photobehavioural responses in different organisms[1,2,3]. Trans-membrane calcium flux initiates a cascade of electrical responses causing depolarization of the cell and controls the flagellar beating pattern[41,42] Another photoreceptor protein (phototropin) has been recently observed to influence eyespot development, ChR1 regulation and phototactic behavior[43]. IFT molecular motors and IFT particles were found to be involved in the trafficking of Chlamyopsin8/Cop[8] (novel rhodopsin identified in this study) and ChR1 into the flagella, in a light dependent manner. Our data leads to a model in which IFT machinery participates in the rhodopsin transport in unicellular eukaryotic green algae Chlamydomonas reinhardtii It suggests that IFT mediated trafficking of rhodopsin is restricted to vertebrates and occurs in lower eukaryotes

Methods

Results

Conclusion