Cytokinesis is the part of the cell division process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and meiosis. During cytokinesis the spindle apparatus partitions and transports duplicated chromatids into the cytoplasm of the separating daughter cells. It thereby ensures that chromosome number and complement are maintained from one generation to the next and that, except in special cases, the daughter cells will be functional copies of the parent cell. After the completion of the telophase and cytokinesis, each daughter cell enters the interphase of the cell cycle.
Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations. It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit muscle, the whole bundle or sheet of smooth muscle cells contracts as a syncytium.
Myosins are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility.
Myosin light-chain kinase also known as MYLK or MLCK is a serine/threonine-specific protein kinase that phosphorylates a specific myosin light chain, namely, the regulatory light chain of myosin II.
Cortactin is a monomeric protein located in the cytoplasm of cells that can be activated by external stimuli to promote polymerization and rearrangement of the actin cytoskeleton, especially the actin cortex around the cellular periphery. It is present in all cell types. When activated, it will recruit Arp2/3 complex proteins to existing actin microfilaments, facilitating and stabilizing nucleation sites for actin branching. Cortactin is important in promoting lamellipodia formation, invadopodia formation, cell migration, and endocytosis.
Aurora kinase B is a protein that functions in the attachment of the mitotic spindle to the centromere.
Transforming protein RhoA, also known as Ras homolog family member A (RhoA), is a small GTPase protein in the Rho family of GTPases that in humans is encoded by the RHOA gene. While the effects of RhoA activity are not all well known, it is primarily associated with cytoskeleton regulation, mostly actin stress fibers formation and actomyosin contractility. It acts upon several effectors. Among them, ROCK1 and DIAPH1 are the best described. RhoA, and the other Rho GTPases, are part of a larger family of related proteins known as the Ras superfamily, a family of proteins involved in the regulation and timing of cell division. RhoA is one of the oldest Rho GTPases, with homologues present in the genomes since 1.5 billion years. As a consequence, RhoA is somehow involved in many cellular processes which emerged throughout evolution. RhoA specifically is regarded as a prominent regulatory factor in other functions such as the regulation of cytoskeletal dynamics, transcription, cell cycle progression and cell transformation.
ROCK1 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.
Myosin light-chain phosphatase, also called myosin phosphatase (EC 3.1.3.53; systematic name [myosin-light-chain]-phosphate phosphohydrolase), is an enzyme (specifically a serine/threonine-specific protein phosphatase) that dephosphorylates the regulatory light chain of myosin II:
Protein phosphatase 1 regulatory subunit 12A is an enzyme that in humans is encoded by the PPP1R12A gene.
Myosin-10 also known as myosin heavy chain 10 or non-muscle myosin IIB (NM-IIB) is a protein that in humans is encoded by the MYH10 gene. Non-muscle myosins are expressed in a wide variety of tissues, but NM-IIB is the only non-muscle myosin II isoform expressed in cardiac muscle, where it localizes to adherens junctions within intercalated discs. NM-IIB is essential for normal development of cardiac muscle and for integrity of intercalated discs. Mutations in MYH10 have been identified in patients with left atrial enlargement.
Citron Rho-interacting kinase is an enzyme that in humans is encoded by the CIT gene.
Anillin is a conserved protein implicated in cytoskeletal dynamics during cellularization and cytokinesis. The ANLN gene in humans and the scraps gene in Drosophila encode Anillin. In 1989, anillin was first isolated in embryos of Drosophila melanogaster. It was identified as an F-actin binding protein. Six years later, the anillin gene was cloned from cDNA originating from a Drosophila ovary. Staining with anti-anillin antibody showed the anillin localizes to the nucleus during interphase and to the contractile ring during cytokinesis. These observations agree with further research that found anillin in high concentrations near the cleavage furrow coinciding with RhoA, a key regulator of contractile ring formation.
Myosin phosphatase Rho-interacting protein is an enzyme that in humans is encoded by the MPRIP gene.
Stress fibers are contractile actin bundles found in non-muscle cells. They are composed of actin (microfilaments) and non-muscle myosin II (NMMII), and also contain various crosslinking proteins, such as α-actinin, to form a highly regulated actomyosin structure within non-muscle cells. Stress fibers have been shown to play an important role in cellular contractility, providing force for a number of functions such as cell adhesion, migration and morphogenesis.
Myosin light chain kinase, smooth muscle also known as kinase-related protein (KRP) or telokin is an enzyme that in humans is encoded by the MYLK gene.
In molecular biology, the FERM domain is a widespread protein module involved in localising proteins to the plasma membrane. FERM domains are found in a number of cytoskeletal-associated proteins that associate with various proteins at the interface between the plasma membrane and the cytoskeleton. The FERM domain is located at the N terminus in the majority of proteins in which it is found.
Calponin 1 is a basic smooth muscle protein that in humans is encoded by the CNN1 gene.
Rho associated coiled-coil containing protein kinase 2 is a protein that in humans is encoded by the ROCK2 gene. Fasudil is an inhibitor of ROCK protein.
In molecular biology, an actomyosin ring or contractile ring, is a prominent structure during cytokinesis. It forms perpendicular to the axis of the spindle apparatus towards the end of telophase, in which sister chromatids are identically separated at the opposite sides of the spindle forming nuclei. The actomyosin ring follows an orderly sequence of events: identification of the active division site, formation of the ring, constriction of the ring, and disassembly of the ring. It is composed of actin and myosin II bundles, thus the term actomyosin. The actomyosin ring operates in contractile motion, although the mechanism on how or what triggers the constriction is still an evolving topic. Other cytoskeletal proteins are also involved in maintaining the stability of the ring and driving its constriction. Apart from cytokinesis, in which the ring constricts as the cells divide, actomyosin ring constriction has also been found to activate during wound closure. During this process, actin filaments are degraded, preserving the thickness of the ring. After cytokinesis is complete, one of the two daughter cells inherits a remnant known as the midbody ring.
