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Biomedical subjects

Robert M Bellin

Publications and source records attributed to Robert M Bellin.

4 recordsLinked to original sources
PubMed2006

Nanoscale intracellular organization and functional architecture mediating cellular behavior.

Cells function based on a complex set of interactions that control pathways resulting in ultimate cell fates including proliferation, differentiation, and apoptosis. The inter-workings of this immensely dense network of intracellular molecules are influenced by more than random protein and nucleic acid distribution where their interactions culminate in distinct cellular function. By probing the design of these biological systems from an engineering perspective, researchers can gain great insight that will aid in building and utilizing systems that are on this size scale where traditional large-scale rules may fail to apply. The organized interaction and gradient distribution in intracellular space imply a structural architecture that modulates cellular processes by influencing biochemical interactions including transport and binding-reactions. One significant structure that plays a role in this modulation is the cell cytoskeleton. Here, we discuss the cytoskeleton as a central and integrating functional structure in influencing cell processes and we describe technology useful for probing this structure. We explain the nanometer scale science of cytoskeletal structure with respect to intracellular organization, mechanotransduction, cytoskeletal-associated proteins, and motor molecules, as well as nano- and microtechnologies that are applicable for experimental studies of the cytoskeleton. This biological architecture of the cytoskeleton influences molecular, cellular, and physiological processes through structured multimodular and hierarchical principles centered on these functional filaments. Through investigating these organic systems that have evolved over billions of years, understanding in biology, engineering, and nanometer-scaled science will be advanced.

Animals↗
PubMed2004

Characterization of an actin-binding site within the talin FERM domain.

Talin is a large cytoskeletal protein that couples integrins to F-actin. Three actin-binding sites (ABS1-3) have been reported: one in the N-terminal head, and two in the C-terminal rod domain. Although the C-terminal ABS3 has been partially characterized, the presence and properties of ABS1 within the talin head are less well defined. We show here that the talin head binds F-actin in vitro and in vivo at a specific site within the actin filament. Thus, purified talin head liberated from gizzard talin by calpain cleavage cosediments with F-actin in a low salt buffer at pH 6.4 (conditions that are optimal for binding intact talin), and using recombinant polypeptides, we have mapped ABS1 to the FERM domain within the talin head. Both the F2 and F3 FERM subdomains contribute to binding, and EGFP-tagged FERM subdomains colocalize with actin stress fibers when expressed in COS cells. High-resolution electron microscopy of actin filaments decorated with F2F3 localizes binding to a site that is distinct from that recognized by members of the calponin-homology superfamily. Finally, we show that the FERM domain can couple F-actin to PIPkin, and by inference to integrins, since they bind to the same pocket in the F3 subdomain. This suggests that the talin FERM domain functions as a linker between PIPkin or integrins and F-actin at sites of cell-matrix adhesions.

Actins↗
PubMed2002

Use of actin isoform-specific antibodies to probe the domain structure in three smooth muscles.

We investigated the location of actin isoforms in relation to each other and to filament attachment sites by studying the edge-to-edge distribution of both immunofluorescence and immunogold probes in smooth muscle cells from three sources. Antibodies to alpha- or alpha,gamma-actin labeled uniformly across smooth muscle cells from each source. Antibodies to beta-cytoplasmic actin were concentrated on and near dense bodies, especially in gizzard smooth muscle, but were also located throughout the filament compartment. Double immunofluorescent labeling with antibodies to alpha- or alpha/gamma- and to beta-actin shows overlap of label at dense bodies and attachment plaques. Double immunofluorescent labeling with antibodies to alpha-actinin and to beta-actin identified dense bodies and attachment plaques as sites of colocalization. Immunogold labeling with anti-desmin was most prominent near dense bodies in the gizzard and was widely dispersed in vas deferens and arterial smooth muscle cells. Our results indicate that there is extensive overlap between the locations of contractile and cytoskeletal elements and, thus, do not support the two-domain model of smooth muscle structure. Tissue-specific organizational motif differences were seen when gizzard, vas deferens, and artery were compared and suggest that one model may not apply to these three smooth muscles.

Actins↗