Endoplasmic reticulum function

Burdakov D., Petersen O.H., and Verkhratsky A. 2005 Intraluminal calcium as a primary regulator of endoplasmic reticulum function. Cell Calcium 38, 303-310. 

In conclusion, a second cytochrome-containing respiratory chain, found in the membranes of the endoplasmic reticulum, functions in the reduction of NAD or NADP. In this sequence the electron is transferred from NADH to cytochrome to cytochrome P450, and finally to oxygen, which can then be used in the mixed oxidation reaction. 

Fagone, P. and Jackowski, S. (2009) Membrane phosphohpid synthesis and endoplasmic reticulum function. J. Lipid Res. 50 Suppl, S311-S316. 

Calcium channels in the plasma membrane activated after receptor-mediated calcium release from intracellular stores. Diese channels are present in many cellular types and play pivotal roles in a multitude of cell functions. It was recently shown that Orai proteins are the pore-forming subunit of CRAC channels. They are activated by STIM proteins that sense the Ca2+ content of the endoplasmic reticulum. 

Cytochrome P450 2C9 is a mixed-function oxidase localized in the endoplasmic reticulum which is responsible for the biotransformation of several nonsteroidal anti-inflammatory diugs, S-warfarin, several sulfonylurea antidiabetics and other diugs. 

Sarcoplasmic reticulum (SR) is a form of the smoothfaced endoplasmic reticulum (ER) in muscles. It functions as an intracellular Ca2+ store for muscle contraction. Ca2+ is energetically sequestered into the SR by Ca2+-pump/sarcoplasmic endoplasmic reticulum Ca2+-ATPase (SERCA) and released via Ca2+ release channels on stimuli (ryanodine receptor in striated muscles and inositol 1,4,5-trisphosphate receptor in most smooth muscles). Endoplasmic reticulum in non-muscle tissues also functions as an intracellular Ca2+ store. 

Blaustein MP, Golovina VA (2001) Structural complexity and functional diversity of endoplasmic reticulum Ca(2-i-) stores. Trends Neurosci 24 602-608 Bonavia R, Bajetto A, Barbero S, Pirani P, Florio T, Schettini G (2003) Chemokines and then-receptors in the CNS expression of CXCL12/SDF-1 and CXCR4 and their role in astrocyte proliferation. Toxicol Lett 139 181-189... 

In the family of cation pumps, only the Na,K-ATPase and H,K-ATPase possess a p subunit glycoprotein (Table II), while the Ca-ATPase and H-ATPase only consist of an a subunit with close to 1 000 amino acid residues. It is tempting to propose that the p subunit should be involved in binding and transport of potassium, but the functional domains related to catalysis in Na,K-ATPase seem to be contributed exclusively by the a subunit. The functional role of the P subunit is related to biosynthesis, intracellular transport and cell-cell contacts. The P subunit is required for assembly of the aj8 unit in the endoplasmic reticulum [20]. Association with a j8 subunit is required for maturation of the a subunit and for intracellular transport of the xP unit to the plasma membrane. In the jSl-subunit isoform, three disulphide... 

Most living cells, including muscle, maintain the cytoplasmic Ca concentration at submicromolar levels, against steep gradients of [Ca ], both at the cell surface and across the endoplasmic reticulum membrane [17]. In the musele cell two membrane systems are primarily involved in this function the sarcoplasmic reticulum and the surface membrane. 

It is well recognized that is an important regulatory element for many cellular processes, and that the major entry pathway for Ca in many cell types is via plasma membrane Ca channels. Ca channels are functional pores in membranes. They exist in plasma membranes, transverse tubule membranes and in intracellular membranes such as the sarcoplasmic and endoplasmic reticulum. Ca channels are normally closed when opened, Ca passively flows through the chan-... 

---