Myomegalin, also known as phosphodiesterase 4D-interacting protein or cardiomyopathy-associated protein 2, is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

that in humans is encoded by the ''PDE4DIP''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. It has roles in the

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

microtubules Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 a ...

from the

centrosome In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle pro ...

. Its name derives from the fact that it is highly expressed in units of tubular

myofibrils A myofibril (also known as a muscle fibril or sarcostyle) is a basic rod-like organelle of a muscle cell. Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils. Each myof ...

known as

sarcomeres A sarcomere (Greek σάρξ ''sarx'' "flesh", μέρος ''meros'' "part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal striated muscle, Skeletal muscles are composed of tubular ...

and is a large protein, at 2,324 amino acids. It was first characterised in 2000.

Structure and function

Myomegalin is mostly composed of

alpha-helix The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand- helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues ear ...

and coiled-coil structures and has domains shared with

microtubule-associated proteins In cell biology, microtubule-associated proteins (MAPs) are proteins that interact with the microtubules of the cellular cytoskeleton. MAPs are integral to: the stability of the cell and its internal structures and the transport of components withi ...

. It has several

isoforms A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some iso ...

, at least two of which have been characterised, CM-MMG and EB-MMG. Myomegalin is necessary for the sufficient

growth Growth may refer to: Biology * Auxology, the study of all aspects of human physical growth * Bacterial growth * Cell growth * Growth hormone, a peptide hormone that stimulates growth * Human development (biology) * Plant growth * Secondary grow ...

from the

centrosomes In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle prog ...

. The CM-MMG isoform binds at the centrosome with

γ-tubulin Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytoske ...

in an

AKAP9 A-kinase anchor protein 9 is a protein that in humans is encoded by the ''AKAP9'' gene. AKAP9 is also known as Centrosome- and Golgi-localized protein kinase N-associated protein (CG-NAP) or AKAP350 or AKAP450 Function The A-kinase anchor prot ...

-dependent manner and on the near side of the

Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ...

, while the EB-MMG isoform binds with

MAPRE1 Microtubule-associated protein RP/EB family member 1 is a protein that in humans is encoded by the ''MAPRE1'' gene. Function The protein encoded by this gene was first identified by its binding to the APC ( Adenomatous polyposis coli) protei ...

at the Golgi apparatus and increases MAPRE1's effects on microtubule growth. Myomegalin, specifically the CM-MMG isoform, is a

paralogue Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a spe ...

CDK5RAP2 CDK5 regulatory subunit-associated protein 2 is a protein that in humans is encoded by the ''CDK5RAP2'' gene. It has necessary roles in the formation and stability of microtubules from the centrosome and has been found to be linked to human brain ...

. Myomegalin depletion in cells does not lead to decreases in γ-tubulin or CDK5RAP2, unlike CDK5RAP2 depletion, and does not appear to affect

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maint ...

through various

spindle Spindle may refer to: Textiles and manufacturing * Spindle (textiles), a straight spike to spin fibers into yarn * Spindle (tool), a rotating axis of a machine tool Biology * Common spindle and other species of shrubs and trees in genus '' Euony ...

anchoring and orientation defects, unlike CDK5RAP2. This indicates that CDK5RAP2 can somewhat serve to compensate for the absence of myomegalin. However, myomegalin-depleted cells have slower

migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum l ...

, since microtubules are crucial for cell motility.

Orthologues Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a sp ...

of myomegalin are seen in

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, wi ...

as far back as

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartila ...

, around 450 million years ago. In

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...

, around 200 million years ago, myomegalin gained an

Olduvai domain The Olduvai domain, known until 2018 as DUF1220 (domain of unknown function 1220) and the NBPF repeat, is a protein domain that shows a striking human lineage-specific (HLS) increase in copy number and appears to be involved in human brain evolu ...

. Olduvai domains have so far only elsewhere been found in NBPF genes in

placental mammals Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...

, many of which are adjacent to myomegalin on chromosome 1, so it is believed that these genes originated from a duplication of myomegalin. Increased NPBF Olduvai domain duplications in humans have been implicated in human brain size evolution.

Interactions

Myomegalin (PDE4DIP) has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizat ...

with

PDE4D cAMP-specific 3',5'-cyclic phosphodiesterase 4D is an enzyme that in humans is encoded by the ''PDE4D'' gene. Function The PDE4D gene is complex and has at least 9 different isoforms that encode functional proteins. These proteins degrade the s ...

History

The protein was discovered in 2000 and was so named because it was highly expressed in rat

heart muscle Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate Muscle tissue, muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striat ...

(units of tubular

) and is a large protein, at 2,324 amino acids.

Structure and function

Interactions

History

See also

References

Further reading