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37-404: ROCKs ( ROCK1 and ROCK2 ) occur in mammals (human, rat, mouse, cow), zebrafish, Xenopus , invertebrates ( C. elegans , mosquito, Drosophila ) and chicken. Human ROCK1 has a molecular mass of 158  kDa and is a major downstream effector of the small GTPase RhoA . Mammalian ROCK consists of a kinase domain, a coiled-coil region and a Pleckstrin homology (PH) domain, which reduces

74-521: A N-terminal kinase domain, a coiled-coil structure and other functional motifs at the C-terminus ROCK is a downstream effector molecule of the Rho GTPase Rho that increases ROCK kinase activity when bound to it. Autoinhibition ROCK activity is regulated by the disruption of an intramolecular autoinhibition. In general, the structure of ROCK proteins consists of an N-terminal kinase domain,

111-416: A bonded atom. This is because some energy is released during bond formation, allowing the entire system to achieve a lower energy state. The bond length, or the minimum separating distance between two atoms participating in bond formation, is determined by their repulsive and attractive forces along the internuclear direction. As the two atoms get closer and closer, the positively charged nuclei repel, creating

148-598: A coiled-coiled region and a PH domain containing a cystein-rich domain (CRD) at the C-terminal. A Rho-binding domain (RBD) is located in close proximity just in front of the PH domain. The kinase activity is inhibited by the intramolecular binding between the C-terminal cluster of RBD domain and the PH domain to the N-terminal kinase domain of ROCK. Thus, the kinase activity is off when ROCK

185-496: A constitutive linear dimer 120 nm in length. According to this new data ROCK does not need to be activated by RhoA or phosphorylation because it is always active, and whether ROCK will phosphorylate its substrates (e.g. myosin regulatory light chain ) depends only on their subcellular localization. There is one other isoform of ROCK known as ROCK2. ROCK2 is located at 2p24 and is highly homologous with ROCK1 with an overall amino acid sequence identity of 65%. The identity in

222-450: A crucial role in tumor cell migration and metastasis. This activated ROCK1 also activates LIM kinase , which, phosphorylates cofilin , inhibiting its actin-depolymerizing activity. This depolymerization results in stabilization of actin filaments and decreased branching which promotes contraction. Cardiac troponin is another ROCK1 substrate that upon phosphorylation causes reduction in tension in cardiac myocytes . ROCK1 also acts as

259-500: A force that attempts to push the atoms apart. As the two atoms get further apart, attractive forces work to pull them back together. Thus an equilibrium bond length is achieved and is a good measure of bond stability. Intramolecular forces are extremely important in the field of biochemistry, where it comes into play at the most basic levels of biological structures. Intramolecular forces such as disulfide bonds give proteins and DNA their structure. Proteins derive their structure from

296-419: A positive ion and a negative ion bound together by electrostatic forces. Electrons in an ionic bond tend to be mostly found around one of the two constituent atoms due to the large electronegativity difference between the two atoms, generally more than 1.9, (greater difference in electronegativity results in a stronger bond); this is often described as one atom giving electrons to the other. This type of bond

333-846: A suppressor of inflammatory cell migration by regulating PTEN phosphorylation and stability. ROCK1 has a diverse range of functions in the body. It is a key regulator of actin-myosin contraction, stability, and cell polarity . These contribute to many progresses such as regulation of morphology, gene transcription, proliferation, differentiation, apoptosis and oncogenic transformation. Other functions involve smooth muscle contraction, actin cytoskeleton organization, stress fiber and focal adhesion formation, neurite retraction, cell adhesion and motility. These functions are activated by phosphorylation of DAPK3 , GFAP , LIMK1 , LIMK2 , MYL9/MLC2 , PFN1 and PPP1R12A . Additionally, ROCK1 phosphorylates FHOD1 and acts synergistically with it to promote SRC-dependent non-apoptotic plasma membrane blebbing . It

370-426: Is a protein serine/threonine kinase also known as rho-associated, coiled-coil-containing protein kinase 1 . Other common names are ROKβ and P160ROCK. ROCK1 is a major downstream effector of the small GTPase RhoA and is a regulator of the actomyosin cytoskeleton which promotes contractile force generation. ROCK1 plays a role in cancer and in particular cell motility , metastasis , and angiogenesis . ROCK1

407-563: Is also required for centrosome positioning and centrosome-dependent exit from mitosis. ROCK1 has been shown to interact with: In humans, the main function of ROCK1 is actomyosin contractility. As mentioned before, this contributes to many proximal progresses such as regulation of morphology, motility, and cell–cell and cell–matrix adhesion. In addition, ROCK kinases influence more distal cellular processes including gene transcription, proliferation, differentiation, apoptosis and oncogenic transformation. Given this diverse range of functions, it

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444-532: Is also the name of the gene that encodes the protein ROCK1, a serine/threonine kinase. ROCK1 is activated when bound to the GTP-bound form of RhoA. The human ROCK1 gene is located on human chromosome 18 with specific location of 18q11.1. The location of the base pair starts at 18,529,703 and ends at 18,691,812 bp and translates into 1354 amino acids . ROCK1 has a ubiquitous tissue distribution, but subcellularly it

481-428: Is any force that binds together the atoms making up a molecule . Intramolecular forces are stronger than the intermolecular forces that govern the interactions between molecules. The classical model identifies three main types of chemical bonds — ionic, covalent, and metallic — distinguished by the degree of charge separation between participating atoms. The characteristics of the bond formed can be predicted by

518-584: Is generally formed between a metal and nonmetal , such as sodium and chlorine in NaCl . Sodium would give an electron to chlorine, forming a positively charged sodium ion and a negatively charged chloride ion. In a true covalent bond , the electrons are shared evenly between the two atoms of the bond; there is little or no charge separation. Covalent bonds are generally formed between two nonmetals. There are several types of covalent bonds: in polar covalent bonds , electrons are more likely to be found around one of

555-621: Is intramolecularly folded. The kinase activity is switched on when Rho-GTP binds to the Rho-binding domain of ROCK, disrupting the autoinhibitory interaction within ROCK, which liberates the kinase domain because ROCK is then no longer intramolecularly folded. Other regulators It has also been shown that Rho is not the only activator of ROCK. ROCK can also be regulated by lipids, in particular arachidonic acid , and protein oligomerization , which induces N-terminal transphosphorylation. Research over

592-530: Is involved in a pathway for smooth muscle contraction. When ROCK1 is activated by binding of GTPase RhoA it produces multiple signaling cascades. For example, RhoA is one of the downstream signaling cascades activated by vascular endothelial growth factor ( VEGF ). ROCK1 acts as a negative regulator of VEGF endothelial cell activation and angiogenesis. ROCK1 activation by RhoA also promotes stabilization of F-actin , phosphorylation of regulatory myosin light chain (MLC) and an increase in contractility, which plays

629-410: Is mainly expressed in the lung , liver , spleen , kidney and testis . However, ROCK2 is distributed mostly in the brain and heart . Protein kinase C and Rho-associated protein kinase are involved in regulating calcium ion intake; these calcium ions, in turn stimulate a myosin light chain kinase, forcing a contraction. Rho-associated protein kinase are serine or threonine kinases that determine

666-497: Is not surprising that ROCK1 has been implicated in numerous aspects of cancer. Recent studies have explored the role of ROCK1 in cancer with particular attention focused on cell motility, metastasis, and angiogenesis. Rho GTPases such as RhoA are highly involved in morphologic changes in cells. When a tumor progresses from invasive to metastatic form it requires that they undergo these dramatic morphologic changes. Therefore, increased expression of RhoA and its downstream effector ROCK1

703-410: Is often observed in human cancers. These cancers are typically more invasive and metastatic phenotypes. Increased expression of RhoA and ROCK1 in endothelial cell migration pathways can cause an increase in angiogenesis and metastatic behavior in tumor cells. It has been suggested that ROCK1 either regulates the expression of angiogenic factors or ROCK1 activation facilitates angiogenesis by increasing

740-437: Is thought to colocalize with the centrosomes . This is consistent with its function as a key modulator of cell motility , tumor cell invasion , and actin cytoskeleton organization. In rats, ROCK1 is expressed in the lung, liver, spleen, kidney, and testis. The ROCK1 structure is a serine/threonine kinase with molecular weight of 158 kDa. It is a homodimer composed of a catalytic kinase domain (residues76-338) located at

777-584: The N-terminus kinase domain. When a substrate such as GTP-bound RhoA binds to the Rho-binding region of the coiled-coil domain, the interactions between the N-terminus and the C-terminus are disrupted, thus activating the protein. Cleavage of the C-terminal inhibitory domain by caspase-3 during apoptosis can also activate the kinase. This view of autoinhibition released by RhoA binding has been challenged by low resolution electron microscopy data showing ROCK to be

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814-411: The Rho-binding domain is 58% and approximately 92% in the kinase domain. The ROCK isoforms are encoded by two different identified genes and are ubiquitously expressed. GTPase-RhoA binding can increase the activity of ROCK1 by 1.5-2-fold. Without RhoA binding, lipids such as arachidonic acid or sphingosine phosphorylcholine can increase ROCK1 activity 5- to 6-fold. These two lipids interact with

851-518: The amino or N-terminus of the protein, a coiled-coil region (residues 425-1100) containing the Rho-binding domain , and a pleckstrin-homology domain (residues 1118-1317) with a cysteine-rich domain. When a substrate is absent, ROCK1 is an autoinhibited loop structure. Enzyme activity of ROCK1 is inhibited when the pleckstrin-homology and Rho-binding domains in the C-terminus independently bind to

888-604: The calcium sensitivity in smooth muscle cells. ROCK plays a role in a wide range of different cellular phenomena, as ROCK is a downstream effector protein of the small GTPase Rho , which is one of the major regulators of the cytoskeleton . 1. ROCK is a key regulator of actin organization and thus a regulator of cell migration as follows: Different substrates can be phosphorylated by ROCKs, including LIM kinase , myosin light chain (MLC) and MLC phosphatase . These substrates, once phosphorylated, regulate actin filament organization and contractility as follows: ROCK inhibits

925-442: The depolymerization of actin filaments indirectly: ROCK phosphorylates and activates LIM kinase , which in turn phosphorylates ADF/cofilin , thereby inactivating its actin-depolymerization activity. This results in the stabilization of actin filaments and an increase in their numbers. Thus, over time actin monomers that are needed to continue actin polymerization for migration become limited. The increased stable actin filaments and

962-441: The electrons are neither completely transferred from one atom to another nor evenly shared. Metallic bonds generally form within a pure metal or metal alloy . Metallic electrons are generally delocalized ; the result is a large number of free electrons around positive nuclei , sometimes called an electron sea. Bonds are formed by atoms so that they are able to achieve a lower energy state. Free atoms will have more energy than

999-482: The extracellular substrate. 2. Other functions and targets 3. Other ROCK targets The two mouse ROCK isoforms, ROCK1 and ROCK2, have high homology . They have 65% amino acid sequences in common and 92% homology within their kinase domains. ROCKs are homologous to other metazoan kinases such as myotonic dystrophy kinase ( DMPK ), DMPK-related cell division control protein 42 ( Cdc42 )-binding kinases (MRCK) and citron kinase. All of these kinases are composed of

1036-424: The intramolecular forces that shape them and hold them together. The main source of structure in these molecules is the interaction between the amino acid residues that form the foundation of proteins. The interactions between residues of the same proteins forms the secondary structure of the protein, allowing for the formation of beta sheets and alpha helices , which are important structures for proteins and in

1073-696: The kinase activation site. Experiments with Y27632 show it is a promising candidate as a therapeutic antihypertensive agent . Fasudil has been used to characterize the role of ROCK1 in vascular function in clinical studies and has been approved for use in Japan for treatment of cerebral vasospasm following subarachnoid hemorrhage . The ROCK1 signaling plays an important role in many diseases including diabetes , neurodegenerative diseases such as Parkinson's disease and amyotrophic lateral sclerosis (ALS), and pulmonary hypertension . Intramolecular force An intramolecular force (from Latin intra- 'within')

1110-496: The kinase activity of ROCKs by an autoinhibitory intramolecular fold if RhoA-GTP is not present. Rat ROCKs were discovered as the first effectors of Rho and they induce the formation of stress fibers and focal adhesions by phosphorylating MLC (myosin light chain). Due to this phosphorylation , the actin binding of myosin II and, thus, the contractility increases. Two mouse ROCK isoforms ROCK1 and ROCK2 have been identified. ROCK1

1147-605: The loss of actin monomers contribute to a reduction of cell migration. ROCK also regulates cell migration by promoting cellular contraction and thus cell-substratum contacts. ROCK increases the activity of the motor protein myosin II by two different mechanisms: Thus in both cases, ROCK activation by Rho induces the formation of actin stress fibers , actin filament bundles of opposing polarity, containing myosin II, tropomyosin, caldesmon and MLC-kinase, and consequently of focal contacts, which are immature integrin -based adhesion points with

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1184-425: The past two decades has shown that ROCK signaling plays an important role in many diseases including cardiovascular disease , neurodegenerative diseases such as Alzheimer's disease , Parkinson's disease , and amyotrophic lateral sclerosis , and cancer . For example, ROCK has been hypothesized to play an important role in the pleiotropic effects of statins . ROCK1/2 along with MRCKα/β kinases have been implicated in

1221-742: The plasticity of cancer cell migration, the phenomenon which bestows survival advantage to the cancer cells during drug treatments ( drug resistance ). Researchers are developing ROCK inhibitors such as RKI-1447 for treating various diseases including cancer. For example, such drugs have potential to prevent cancer from spreading by blocking cell migration, stopping cancer cells from spreading into neighboring tissue. ROCK1 1S1C , 2ESM , 2ETK , 2ETR , 2V55 , 3D9V , 3NCZ , 3NDM , 3O0Z , 3TV7 , 3TWJ , 3V8S , 4L2W , 4W7P , 4YVC , 4YVE , 5BML 6093 19877 ENSG00000067900 ENSMUSG00000024290 Q13464 P70335 NM_005406 NM_009071 NP_005397 NP_033097 ROCK1

1258-444: The plasticity of the tumor. By reducing the strength of cell-cell interactions and aiding the movement of tumor cells, ROCK1 may enable endothelial cells to penetrate the tumor mass more easily. ROCK1 inhibitors might be used in cancer therapy for: ROCK1 inhibition for cancer treatment has not been approved for standard therapy use. Y27632 and Fasudil are examples of ROCK1 inhibitors. Both inhibit ROCK1 by competing with ATP for

1295-590: The pleckstrin-homology domain, thus disrupting its ability to inhibit ROCK1. G-protein RhoE binds to the N-terminus of ROCK1 and inhibits its activity by preventing RhoA binding. Small G-proteins, Gem and Rad , have been shown to bind and inhibit ROCK1 function, but their mechanism of action is unclear. ROCK1 phosphorylation sites are at RXXS/T or RXS/T. More than 15 ROCK1 substrates have been identified and activation from these substrates most often leads to actin filament formation and cytoskeleton rearrangements. MYPT-1

1332-479: The properties of constituent atoms, namely electronegativity. They differ in the magnitude of their bond enthalpies , a measure of bond strength, and thus affect the physical and chemical properties of compounds in different ways. % of ionic character is directly proportional difference in electronegativity of bonded atom. An ionic bond can be approximated as complete transfer of one or more valence electrons of atoms participating in bond formation, resulting in

1369-406: The two atoms, whereas in nonpolar covalent bonds, electrons are evenly shared. Homonuclear diatomic molecules are purely covalent. The polarity of a covalent bond is determined by the electronegativities of each atom and thus a polar covalent bond has a dipole moment pointing from the partial positive end to the partial negative end. Polar covalent bonds represent an intermediate type in which

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