Transmembrane and Coiled-Coil Domain Family 1 Is a Novel Protein of the Endoplasmic Reticulum

Chao Zhang,Yik-Shing Kho,Gary K H Ng,Robert Z Qi,Pang-Chui Shaw,Yan Ting Chiang,Zhe Wang,Yuzhuo Wang,F Gisou Van Der Goot

doi:10.1371/journal.pone.0085206

Abstract

The endoplasmic reticulum (ER) is a continuous membrane network in eukaryotic cells comprising the nuclear envelope, the rough ER, and the smooth ER. The ER has multiple critical functions and a characteristic structure. In this study, we identified a new protein of the ER, TMCC1 (transmembrane and coiled-coil domain family 1). The TMCC family consists of at least 3 putative proteins (TMCC1–3) that are conserved from nematode to human. We show that TMCC1 is an ER protein that is expressed in diverse human cell lines. TMCC1 contains 2 adjacent transmembrane domains near the C-terminus, in addition to coiled-coil domains. TMCC1 was targeted to the rough ER through the transmembrane domains, whereas the N-terminal region and C-terminal tail of TMCC1 were found to reside in the cytoplasm. Moreover, the cytosolic region of TMCC1 formed homo- or hetero-dimers or oligomers with other TMCC proteins and interacted with ribosomal proteins. Notably, overexpression of TMCC1 or its transmembrane domains caused defects in ER morphology. Our results suggest roles of TMCC1 in ER organization.

Highlights

The endoplasmic reticulum (ER) is a continuous network of membranes in eukaryotic cells that extends throughout the cytoplasm
We have shown that TMCC1 is an evolutionarily conserved protein and have provided first evidence of TMCC1 expression in human cells
Using immunolabeling and ER-isolation experiments, we have demonstrated that TMCC1 is a rough ER protein

Summary

Introduction

The endoplasmic reticulum (ER) is a continuous network of membranes in eukaryotic cells that extends throughout the cytoplasm. The functions of the ER, one of the largest organelles in cells, have been studied extensively, including the translocation of proteins across the ER membrane [1,2], the folding of proteins in the ER lumen [3,4], the transport of proteins from ER to the Golgi apparatus [5,6], the synthesis of lipids and steroids [7,8], and the regulation of cellular Ca2+ concentrations [9,10]. Rough ER, defined by the presence of membrane-bound ribosomes, is responsible for the translation, translocation, and folding of membrane and secretory proteins. Smooth ER, defined by the absence of membrane-bound ribosomes, is required for lipid synthesis, steroid metabolism, and regulation of Ca2+ concentrations in cells

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Results

Conclusion