Differential distribution of subsets of myofibrillar proteins in cardiac nonstriated and striated myofibrils.

Schultheiss, Thomas M.; Lin, Zhenwu; Lu, Mei-Hua; Murray, John M.; Fischman, Donald A.; Weber, Klaus; Takao, Masaki; Imamura, Michihiro; Holtzer, H.

doi:10.1083/jcb.110.4.1159

Cited by 201 publications

(149 citation statements)

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“…On the other hand, in cardiac myocytes, it is not associated with the myofibrils until after the addition of a-actinin (23). Additionally, myomesinis only found associated with striated myofibrils in chicken cardiac myocytes, whereas in skeletal myogenic cells, it is found associated with both nonstriated premyofibrils and mature striated myofibrils (28).…”

mentioning

confidence: 87%

Models of Thin Filament Assembly in Cardiac and Skeletal Muscle.

Gregorio

1997

Cell Struct. Funct.

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ABSTRACT. The assembly and functional characteristics of many contractile proteins are different in skeletal and cardiac muscle. Twomodels for thin filament assembly are consistent with observations from recent studies focused on determining the functional significance of actin filament capping in primary cultures of embryonic chick myogenic cells and cardiac myocytes. Future experiments will test the validity of the proposed models for in vivo embryonic development.Perfectly aligned myofibrils in striated muscle represent one of the most highly ordered macromolecular structures found in eukaryotic cells. The assembly of contractile proteins into myofibrils is a complex process that requires coordinate synthesis of the constituent proteins, polymerization of actin and myosin (and many associated proteins) into thin and thick filaments, respectively, and association of the two filament systems into highly organized sarcomeres. Newly assembled sarcomeres consist of parallel arrays of approximately 1.0 m-long thin filaments that interdigitate with laterally aligned 1.6 fim long thick filaments. Rodlike tropomyosin molecules are associated with each other head-totail, forming two polymers per thin filament. Each tropomyosin molecule binds one troponin complex (composed of troponins T, I and C); together they mediate the calcium regulation of myosin ATPase(35). Thin filaments are polarized in muscle sarcomeres with the barbed ends crosslinked by a-actinin and anchored at the Z disk, and the pointed ends terminating in the A band and overlapping with the bipolar myosin filaments (ll). ("Barbed" and "pointed" ends of actin filaments refer to the orientation of arrowheads generated by myosin sub fragment 1 binding to actin filaments and are the fast-growing and the slow-growing ends of the filaments, respectively.)

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confidence: 87%

Models of Thin Filament Assembly in Cardiac and Skeletal Muscle.

Gregorio

1997

Cell Struct. Funct.

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“…Four major hypotheses seeking to explain the mechanism of myofibril formation have been recently reviewed by Sanger et al (2005). These hypothetic models can be summarized as following: (1) template model that considers stress fiber-like structures as templates or scaffolds for assembly of myofibrils (Dlugosz et al 1984); (2) the "stitching" model in which the actin filaments and Z-bands assemble independently from myosin filaments (Schultheiss et al 1990;Holtzer et al 1997;Ojima et al 1999); (3) premyofibril model assuming the formation of premyofibrils as immediate structural precursors of myofibrils (Rhee et al 1994;Du et al 2003;Sanger 2005), and (4) direct assembly of myofibrils without any intermediate structures [for literature see Ehler et al (1999Ehler et al ( , 2004]. …”

Section: Introductionmentioning

confidence: 99%

Early incorporation of obscurin into nascent sarcomeres: implication for myofibril assembly during cardiac myogenesis

Borisov

Martynova

Russell

2008

Histochem Cell Biol

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Obscurin is a recently identified giant multidomain muscle protein whose functions remain poorly understood. The goal of this study was to investigate the process of assembly of obscurin into nascent sarcomeres during the transition from non-striated myofibril precursors to striated structure of differentiating myofibrils in cell cultures of neonatal rat cardiac myocytes. Double immunofluorescent labeling and high resolution confocal microscopy demonstrated intense incorporation of obscurin in the areas of transition from non-striated to striated regions on the tips of developing myofibrils and at the sites of lateral fusion of nascent sarcomere bundles. We found that obscurin rapidly and precisely accumulated in the middle of the A-band regions of the terminal newly assembled half-sarcomeres in the zones of transition from the continuous, non-striated pattern of sarcomeric α-actinin distribution to cross-striated structure of laterally expanding nascent Z-discs. The striated pattern of obscurin typically ended at these points. This occurred before the assembly of morphologically differentiated terminal Z-discs of the assembling sarcomeres on the tips of growing myofibrils. The presence of obscurin in the areas of the terminal Z-discs of each new sarcomere was detected at the same time or shortly after complete assembly of sarcomeric structure. Many non-striated fibers with very low concentration of obscurin were already immunopositive for sarcomeric actin and myosin. This suggests that obscurin may serve for organization and alignment of myofilaments into the striated pattern. The comparison of obscurin and titin localization in these areas showed that obscurin assembly into the A-bands occurred soon after or concomitantly with incorporation of titin. Electron microscopy of growing myofibrils demonstrated intense formation and integration of myosin filaments into the "open" half-assembled sarcomeres in the areas of the terminal Z-I structures and at the lateral surfaces of newly formed, terminally located nascent sarcomeres. This process progressed before the assembly of the second-formed, terminal Z-discs of new sarcomeres and before the development of ultrastructurally detectable mature M-lines that define the completion of myofibril assembly, which supports the data of immunocytochemical study. Abundant non-aligned sarcomeres in immature myofibrils located on the growing tips were spatially separated and underwent the transition to the registered, aligned pattern. The sarcoplasmic reticulum, © Springer-Verlag 2008 aborisov@umich.edu. This paper is dedicated to the memory of Professor Pavel P. Rumyantsev (1927Rumyantsev ( -1988, a pioneer in studies of cardiac muscle differentiation, who is a lasting inspiration to all who worked with him. the organelle known to interact with obscurin, assembled around each new sarcomere. These results suggest that obscurin is directly involved in the proper positioning and alignment of myofilaments within nascent sarcomeres and in the establishment of the registered ...

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“…It is thought to participate in thick filament assembly by binding myosin and titin, thus probably contributing to sarcomere stability (Schultheiss et al 1990). The protein also has regulatory activities (Moos and Feng 1990;Schlender and Bean 1991).…”

Section: Characterization Of Specific Myh7 Mutationsmentioning

confidence: 99%