Page last updated: 2024-10-24

sarcoplasmic reticulum lumen

Definition

Target type: cellularcomponent

The volume enclosed by the membranes of the sarcoplasmic reticulum. [GOC:rph]

The sarcoplasmic reticulum (SR) lumen is a specialized intracellular compartment within muscle cells, specifically skeletal and cardiac muscle. It is a network of interconnected tubules and cisternae that surrounds the myofibrils, the contractile units of muscle fibers. The lumen of the SR is filled with a fluid that contains a high concentration of calcium ions (Ca2+), which are essential for muscle contraction.

**Here are some detailed characteristics of the SR lumen:**

* **Calcium Store:** The SR lumen is the primary intracellular storage site for Ca2+ in muscle cells. The Ca2+ is actively pumped into the lumen by SR Ca2+-ATPase pumps, maintaining a high concentration gradient across the SR membrane.

* **Release and Uptake of Calcium:** During muscle contraction, a nerve impulse triggers the release of Ca2+ from the SR lumen into the sarcoplasm, the cytoplasm of muscle cells. This Ca2+ binds to troponin, a protein associated with the thin filaments of the myofibrils, initiating muscle contraction. Following contraction, Ca2+ is actively pumped back into the SR lumen, restoring the resting state of the muscle.

* **Specialized Proteins:** The SR lumen contains several specialized proteins involved in Ca2+ handling and regulation, including:
* **Calsequestrin:** A high-capacity Ca2+-binding protein that buffers Ca2+ in the lumen, preventing excessive accumulation.
* **Sarcolipin:** A small protein that regulates the activity of the SR Ca2+-ATPase, influencing Ca2+ uptake.
* **Junctin and Triadin:** Proteins that interact with the SR Ca2+-ATPase and ryanodine receptor, facilitating Ca2+ release and uptake.

* **Tubular Network:** The SR lumen forms a complex network of interconnected tubules, including:
* **Terminal Cisternae:** Expanded regions of the SR located at the junctions between A and I bands in the myofibrils. They are responsible for the localized release of Ca2+ during muscle contraction.
* **Longitudinal Tubules:** Run parallel to the myofibrils, connecting the terminal cisternae and facilitating Ca2+ diffusion throughout the SR network.

* **Critical Role in Muscle Contraction:** The SR lumen plays a vital role in muscle contraction by providing the rapid release and uptake of Ca2+, enabling efficient and precise control of muscle activity.

* **Structural Integrity:** The SR lumen is enclosed by a specialized membrane that maintains its structural integrity and regulates the flow of molecules between the lumen and the sarcoplasm.

* **Interactions with Other Cellular Components:** The SR lumen interacts closely with other cellular components involved in muscle contraction, including the sarcolemma (muscle cell membrane) and the transverse tubules (T-tubules), which transmit the nerve impulse to the SR.

* **Regulation of Muscle Function:** The SR lumen contributes to the regulation of muscle function by modulating Ca2+ levels and influencing the speed and duration of muscle contraction.

**In summary, the sarcoplasmic reticulum lumen is a specialized intracellular compartment critical for muscle contraction by serving as a calcium store, regulating calcium release and uptake, and interacting with other cellular components to ensure proper muscle function.**
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Proteins (2)

ProteinDefinitionTaxonomy
EndoplasminAn endoplasmin that is encoded in the genome of dog. [OMA:P41148, PRO:DAN]Canis lupus familiaris (dog)
EndoplasminAn endoplasmin that is encoded in the genome of human. [PRO:DAN]Homo sapiens (human)

Compounds (27)

CompoundDefinitionClassesRoles
adenosine diphosphateAdenosine Diphosphate: Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.adenosine 5'-phosphate;
purine ribonucleoside 5'-diphosphate
fundamental metabolite;
human metabolite
2-chloroadenosine5-chloroformycin A: structure given in first sourcepurine nucleoside
adenosinequinquefolan B: isolated from roots of Panax quinquefolium L.; RN not in Chemline 10/87; RN from Toxlitadenosines;
purines D-ribonucleoside
analgesic;
anti-arrhythmia drug;
fundamental metabolite;
human metabolite;
vasodilator agent
adenosine-5'-carboxylic acidpurine nucleoside
adenosine 5'-carboxamideadenosine 5'-carboxamide: structure
5'-n-methylcarboxamideadenosine5'-N-methylcarboxamideadenosine: RN given refers to (beta-D)-isomer
n-methyladenosineN-methyladenosine: is a inhibitor of cell differentiation

N(6)-methyladenosine : A methyladenosine compound with one methyl group attached to N(6) of the adenine nucleobase.
methyladenosine
ethyl adenosine-5'-carboxylateethyl adenosine-5'-carboxylate: potent vasoactive substance; RN given refers to parent cpd
adenosine 5'-phosphoramidateadenosine 5'-phosphoramidate : The phosphoramadite analogue of AMP.organic phosphoramidateMycoplasma genitalium metabolite
adenosine-5'-(n-ethylcarboxamide)Adenosine-5'-(N-ethylcarboxamide): A stable adenosine A1 and A2 receptor agonist. Experimentally, it inhibits cAMP and cGMP phosphodiesterase activity.

N-ethyl-5'-carboxamidoadenosine : A derivative of adenosine in which the 5'-hydroxymethyl group is replaced by an N-ethylcarboxamido group.
adenosines;
monocarboxylic acid amide
adenosine A1 receptor agonist;
adenosine A2A receptor agonist;
antineoplastic agent;
EC 3.1.4.* (phosphoric diester hydrolase) inhibitor;
vasodilator agent
adenosine-5'-(N-propyl)carboxamideadenosine-5'-(N-propyl)carboxamide : A monocarboxylic acid amide that is the propyl amide of adenosine 5'-carboxylic acid.adenosines;
monocarboxylic acid amide
geldanamycin1,4-benzoquinones;
ansamycin;
carbamate ester;
organic heterobicyclic compound
antimicrobial agent;
antineoplastic agent;
antiviral agent;
cysteine protease inhibitor;
Hsp90 inhibitor
17-(dimethylaminoethylamino)-17-demethoxygeldanamycin17-(dimethylaminoethylamino)-17-demethoxygeldanamycin: structure in first source

alvespimycin : A 19-membered macrocyle that is geldanamycin in which the methoxy group attached to the benzoquinone moiety has been replaced by a 2-(N,N-dimethylamino)ethylamino group.
1,4-benzoquinones;
ansamycin;
carbamate ester;
secondary amino compound;
tertiary amino compound
Hsp90 inhibitor
tanespimycinCP 127374: analog of herbimycin A1,4-benzoquinones;
ansamycin;
carbamate ester;
organic heterobicyclic compound;
secondary amino compound
antineoplastic agent;
apoptosis inducer;
Hsp90 inhibitor
1-aminoadenosine1-aminoadenosine: structure
9h-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-n-(1-methylethyl)-9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-: an epichaperome (purine-scaffold) inhibitor; structure in first source
5'-amino-5'-deoxyadenosine
ipi 49317-aminogeldanamycin: structure in first source
n-cyclopropyl adenosine-5'-carboxamide
ec 144EC 144: structure in first source
at 13387(2,4-dihydroxy-5-isopropylphenyl)-(5-(4-methylpiperazin-1-ylmethyl)-1,3-dihydroisoindol-2-yl)methanone: structure in first source

onalespib : A member of the class of isoindoles that is isoindole in which the amino group has been acylated by a 2,4-dihydroxy-5-isopropylbenzoyl group and in which position 5 of the isoidole moiety has been substituted by a (4-methylpiperazin-1-yl)methyl group. A second-generation Hsp90 inhibitor.
benzamides;
isoindoles;
N-alkylpiperazine;
resorcinols;
tertiary carboxamide
antineoplastic agent;
Hsp90 inhibitor
cnf 20242-aminopurines;
aromatic ether;
organochlorine compound;
pyridines
antineoplastic agent;
Hsp90 inhibitor
snx 2112SNX 2112: an orally available small molecule Hsp90 inhibitor; structure in first source
debio 0932CUDC 305: an Hsp90 inhibitor with antineoplastic activity; structure in first source
tas-116
ver 52296luminespib : A monocarboxylic acid amide obtained by formal condensation of the carboxy group of 5-(2,4-dihydroxy-5-isopropylphenyl)-4-[4-(morpholin-4-ylmethyl)phenyl]-1,2-oxazole-3-carboxylic acid with the amino group of ethylamine.aromatic amide;
isoxazoles;
monocarboxylic acid amide;
morpholines;
resorcinols
angiogenesis inhibitor;
antineoplastic agent;
Hsp90 inhibitor
sta 9090ring assembly;
triazoles