Identification of I-Plastin, a Human Fimbrin Isoform Expressed in Intestine and Kidney

Abstract

The complete cDNA sequence of human intestine-specific plastin (I-plastin) was determined from a clone derived by PCR. It consists of a 97-bp 5' untranslated region, a 1,887-bp coding region, and a 1,655-bp 3' untranslated region. The coding region predicts a 629-residue polypeptide whose sequence displays 86, 75, and 73% identities with chicken intestine fimbrin, human T-plastin, and human L-plastin, respectively. Recombinant I-plastin cross-linked actin filaments into bundles in the absence but not in the presence of calcium. The I-plastin gene was mapped by PCR to human chromosome 3; the L- and T-plastin genes were previously mapped to chromosomes 13 and X, respectively. I-plastin mRNA was detected in the small intestine, colon, and kidneys; relatively lower levels of expression were detected in the lungs and stomach. In contrast, L-plastin expression was restricted to the spleen and other lymph node-containing organs, while T-plastin was expressed in a variety of organs, including muscle, brain, uterus, and esophagus. In contrast to the situation for the intestine, high levels of L- and T-plastin mRNAs were detected in Caco-2, a human colon-derived cell line. Immunofluorescence microscopy detected I-plastin in the brush border of the small intestine and colon. These results identify I-plastin as the human homolog of chicken intestine fimbrin and as a third plastin isoform in humans.

Ataxin-2 and huntingtin interact with endophilin-A complexes to function in plastin-associated pathways

“…For visualization of HA-tagged ATX2 proteins, cells were treated with an antibody directed against the HA-tag (1:400, Roche). The isoforms, L-and T-plastin, were stained with the polyclonal antibodies, a-L-plastin or a-T-plastin using a dilution of 1:200 (93). Subsequently, cells were washed in PBS/0.1% Triton X-100 and incubated with the corresponding secondary antibodies, FITC-conjugated a-mouse IgG (1:400, Dianova) or Cy3conjugated a-rabbit IgG (1 : 400, Dianova).…”

T-plastin is essential for basement membrane assembly and epidermal morphogenesis

“…The single plastin of budding yeast, Sac6p, plays a key role in morphogenesis, endocytosis, and polarity (22,23). Mammals have three plastins: I-plastin (encoded by Pls1), present in the intestine and in the kidney; L-plastin (encoded by Lcp1), present in hematopoietic cells; and T-plastin (encoded by Pls3), which is detected in solid tissues, including the skin epidermis (24,25). Loss-of-function studies in mice have shown that L-plastin is essential for the development and function of T cells (26), whereas I-plastin plays a role in the function of intestinal microvilli (27) and stereocilia (28).…”

Fluctuating semiflexible polymer ribbon constrained to a ring

“…The semiflexible polymers constituting the cell's cytoskeleton determine morphology and elasticity of the cell. By use of binding proteins the polymers organize into bundles of closely packed filaments, which form the building blocks for a variety of cellular processes such as filopodia, villi or cilia [1,2,3,4]. Recent investigations of the mechanical properties of polymer bundles [5] pose the question for a coarse-grained description of their mechanics beyond the macroscopic models for semiflexible polymers such as the Kratky-Porod model [6] and its continuous description [7], which represent the polymer by a space curve with a single material parameter.…”