Identification and overlapping expression of multiple unconventional myosin genes in vertebrate cell types.

Abstract

Myosin divers In the human epi cell line Caco-2Ba, the porcine pihal Cell line LLC PK1 (CL-4)9human peripheral blood leukocytes, and human liver was analyzed. PCR amplification yielded [8][9][10][11] Eukaryotes display a broad array of motility phenomena, ranging from muscle-driven movement to translocation of intracellular organelles. The mechanisms underlying these phenomena are not entirely clear, but it is generally thought that "molecular motors," such as kinesins, dyneins, and myosins, act at cytoskeletal-cytoskeletal and cytoskeletalmembrane interfaces to power organism and cellular movements (1-4). These motors are represented by multiple members in eukaryotes (4, 5), each of which is presumed to play one or more roles during the life of the organism. For example, the fruit fly is known to have at least 6 (6) and possibly as many as 30 (7) kinesins. A unicellular organism, Dictyostelium discoideum, has a minimum offive myosins (8, 9) and probably more than nine (10, 47).Thus, within an organism, multiple diverse molecular motors are the rule. For myosins, phylogenetic analyses have revealed the existence of eight classes (11-13), termed either conventional (filament-forming myosins II) or unconventional (apparently nonfilamentous myosins I and III-VIII) (14). Although evidence indicates that many ofthe unconventional myosin classes will be represented in a given organism (5, 15), to our knowledge, in no case has the number of myosins expressed in a metazoan cell type been determined. Consequently, studies concerning actin-based motility in metazoan cells are complicated by limited information on cellular myosin diversity. We therefore analyzed myosin diversity in two epithelial cell lines, Caco2BBe (16) and LLC-PK1 (17), and in human leukocytes and liver.1 Surprisingly, these cell types express six myosin classes, most of which have at least two representatives. The results challenge the standard "myosin I vs.

Myosin V and iNOS expression is enhanced in J774 murine macrophages treated with IFN-gamma

“…Our results also demonstrate that a single cell type can present numerous myosins. This agrees with Bement et al (17), who documented the expression of at least a dozen myosins within a given vertebrate cell type. There was no evidence of degradation products, probably due to the method of preparation of a homogenate from fresh cells and to the use of protease inhibitors.…”

Myo3A, One of Two Class III Myosin Genes Expressed in Vertebrate Retina, Is Localized to the Calycal Processes of Rod and Cone Photoreceptors and Is Expressed in the Sacculus

“…A myosin PCR screen was performed on bass retina/RPE cDNA using the degenerate myosin primers ATP-3 and EAF-A (Bement et al, 1994) to amplify the myosins expressed in these tissues. The resultant ϳ150 -base pair PCR products were subcloned, sequenced, and analyzed against GenBank, EMBL, DDBJ, and PDB sequences using the BLAST Network Service of the National Center for Biotechnology Information.…”

Truncated Brush Border Myosin I Affects Membrane Traffic in Polarized Epithelial Cells

“…All myosin Is exhibit a positively charged region in their tail that has been shown to bind directly to anionic lipids. However, myosin Is can be divided into distinct subclasses based upon sequence homologies in their head and tail domains (18,25,26). It has been suggested that one subclass, which is identified to date only in metazoans and encompasses myosin I alpha (MMIa) and brush border myosin I (BBMI), is involved in endocytosis (22,24).…”