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Xiong Liu

Publications and source records attributed to Xiong Liu.

25 records · Page 2Linked to original sources
PubMed2004

Subdomain organization of the Acanthamoeba myosin IC tail from cryo-electron microscopy.

Acanthamoeba myosin IC (AMIC) is a single-headed myosin comprised of one heavy chain (129 kDa) and one light chain (17 kDa). The heavy chain has head, neck (light chain-binding), and tail domains. The tail consists of four subdomains: a basic region (BR) (23 kDa) and two Gly/Pro/Ala-rich (GPA) regions, GPA1 (6 kDa) and GPA2 (15 kDa), flanking an Src homology 3 region (6 kDa). Although the AMIC head is similar in sequence, structure, and function (ATPase motor) to other myosin heads, the organization of the tail has been less clear as has its function beyond an assumed role in binding interaction partners, e.g., the BR has a membrane affinity and the GPA components bind F-actin in an ATP-independent manner. To investigate the spatial arrangement of subdomains in the tail, we have used cryo-electron microscopy and image reconstruction to compare actin filaments decorated with WT AMIC and tail-truncated mutants of various lengths. The BR forms an oval-shaped feature, approximately 40 A long, that diverges obliquely from the head, extending azimuthally around the actin filament and toward its barbed end. GPA2 and GPA1 are located together on the inner (actin-proximal) side of the tail, close enough to act in concert in binding the same or another actin filament. The outer face of the BR is strategically exposed for membrane or vesicle binding.

Acanthamoeba↗
PubMed2004

Effect of inhibition of EBV-encoded latent membrane protein-1 by small interfering RNA on EBV-positive nasopharyngeal carcinoma cell growth.

OBJECTIVE: To evaluate the feasibility of using small interfering RNA (siRNA) for selective inhibiting latent membrane protein-1 (LMP1) expression in Epstein-Barr virus (EBV)-positive nasopharyngeal carcinoma (NPC) cell line C611, and observe the effects of LMP1 gene silencing on the NPC cell growth. METHODS: Four synthesized double-strand siRNA were respectively transfected into NPC cells, using Oligofectamine reagent. The subsequent changes in LMP1 mRNA level were determined by semi-quantitative reverse transcriptase (RT)-PCR. Flow cytometry and MTT assay were employed to examine the alterations in cell cycle and cell proliferation. RESULTS: The most effective sequence was identified among the 4 candidate siRNAs, and its single dose caused nearly 90% loss of LMP1 mRNA in C611 cells, with sustained specific inhibition for 96 h following a re-transfection. LMP1 siRNA treatment resulted in cell cycle arrest at G(0)-G(1) phase, accompanied by a reduction of cell proliferation by 33%, whereas EBV-negative NPC cells appeared unaffected. CONCLUSIONS: EBV-encoded LMP-1 is vulnerable to RNA interference and selective inhibition of LMP1 suppresses the proliferation of EBV-positive NPC cells, a finding that sheds light on the possible use of RNA interference in further investigations of LMP1 and for therapeutic purposes of EBV-related NPC.

Apoptosis↗
PubMed2004

[Clinical evaluation of 18-fluorine fluorodeoxyglucose positron emission tomography-CT imaging in head and neck tumors].

OBJECTIVE: To study the clinical value of 18-fluorine fluorodeoxyglucose (18 F-FDG) positron emission tomography (PET)-CT imaging in diagnosis and detection of primary tumors and suspicious recurrence in head and neck cancers. METHODS: Twenty-seven patients with primary tumors or metastases in head and neck underwent 18F-FDG PET-CT imaging, and compared with clinical data. RESULTS: 1. In 4 NPC diagnosed pre-radiation patients the 18F-FDG PET-CT imaging in nasopharynx was all positive, 2 of them were detected with neck lymph node metastases, which were confirmed later histopathologically. In 12 NPC cases after radiation, 4 were not found any evidence of tumor with PET-CT imaging and clinically, 4 were detected neck recurrence and confirmed histopathologically, 2 had remote metastases confirmed by other imaging, 2 were detected and confirmed recurrence in primary sites and one of them in regional and remote site. 2. In 4 neck metastatic patients with unknown primary tumor, the primary tumors were all identified, 3 of them were confirmed histopathologically. 3. Seven patients with other head and neck tumors after therapy underwent 18F-FDG PET-CT imaging. Two patients had no evidence of recurrence. Five patients were detected recurrence or metastases, 4 of them were confirmed histopathologically, one of them refused biopsy. CONCLUSIONS: With metabolic image of PET and anatomic image of CT, 18F-FDG PET-CT is a kind of very useful way in diagnosing primary tumor and detecting the recurrence and metastases in patients with head and neck tumor.

Female↗
PubMed2003

Dictyostelium and Acanthamoeba myosin II assembly domains go to the cleavage furrow of Dictyostelium myosin II-null cells.

How myosin II localizes to the cleavage furrow of dividing cells is largely unknown. We show here that a 283-residue protein, assembly domain (AD)1, corresponding to the AD in the tail of Dictyostelium myosin II assembles into bundles of long tubules when expressed in myosin II-null cells and localizes to the cleavage furrow of dividing cells. AD1 mutants that do not polymerize in vitro do not go to the cleavage furrow in vivo. An assembly-competent polypeptide corresponding to the C-terminal 256 residues of Acanthamoeba myosin II also goes to the cleavage furrow of Dictyostelium myosin II-null cells. When overexpressed in wild-type cells, AD1 colocalizes with endogenous myosin II (possibly as a copolymer) in interphase, motile, and dividing cells and under caps of Con A receptors but has no effect on myosin II-dependent functions. These results suggest that neither a specific sequence, other than that required for polymerization, nor interaction with other proteins is required for localization of myosin II to the cleavage furrow.

Acanthamoeba↗
PubMed2003

[Expression of matrix metalloproteinase-2 in hypopharyngeal carcinoma and its clinical significance].

OBJECTIVE: To study the relationship between matrix metalloproteinase-2(MMP-2) and the biological behavior, metastasis and prognosis of hypopharyngeal carcinoma. METHODS: Two-step immunohistochemical method was used to examine the expression of MMP-2 mAb in 32 specimens of hypopharyngeal carcinoma tissues and adjacent normal mucosa. Statistical comparison was performed after grouping. RESULTS: It was found that the positivity rate for MMP-2 in the hypopharyngeal carcinoma tissues was 53.1%(17/32). Significant differences were noted when the expression levels of the mAb were compared between the normal mucosa adjacent to the carcinomas and the carcinomatous tissue, and between non-metastatic carcinomas and those with cervical lymph node metastasis. Patients with a positive result had obviously lower 3-year survival rate than those with negative results. CONCLUSION: MMP-2 may play a role in the lymph node metastasis of hypopharyngeal carcinoma, and is likely to be indicative of the patients' prognosis.

Humans↗
PubMed2002

Tail chimeras of Dictyostelium myosin II support cytokinesis and other myosin II activities but not full development.

Dictyostelium lacking myosin II cannot grow in suspension culture, develop beyond the mound stage or cap concanavalin A receptors and chemotaxis is impaired. Recently, we showed that the actin-activated MgATPase activity of myosin chimeras in which the tail domain of Dictyostelium myosin II heavy chain is replaced by the tail domain of either Acanthamoeba or chicken smooth muscle myosin II is unregulated and about 20 times higher than wild-type myosin. The Acanthamoeba chimera forms short bipolar filaments similar to, but shorter than, filaments of Dictyostelium myosin and the smooth muscle chimera forms much larger side-polar filaments. We now find that the Acanthamoeba chimera expressed in myosin null cells localizes to the periphery of vegetative amoeba similarly to wild-type myosin but the smooth muscle chimera is heavily concentrated in a single cortical patch. Despite their different tail sequences and filament structures and different localization of the smooth muscle chimera in interphase cells, both chimeras support growth in suspension culture and concanavalin A capping and colocalize with the ConA cap but the Acanthamoeba chimera subsequently disperses more slowly than wild-type myosin and the smooth muscle chimera apparently not at all. Both chimeras also partially rescue chemotaxis. However, neither supports full development. Thus, neither regulation of myosin activity, nor regulation of myosin polymerization nor bipolar filaments is required for many functions of Dictyostelium myosin II and there may be no specific sequence required for localization of myosin to the cleavage furrow.

Acanthamoeba↗