An undifferentiated carcinoma (UC) of the gall bladder behaves aggressively and has a grave prognosis. Small cell type undifferentiated carcinoma of the gall bladder is a rare variant. This paper reports a case of UC of gall bladder with PAS-positive diastase-resistant eosinophilic hyaline globules present as liver mass (on imaging) in a male patient. The microscopic findings of the liver and gall bladder after a right tri-segmentectomy showed an un-differentiated malignant neoplasm composed of cells with round to oval nuclei, prominent nucleoli, and scanty neoplasm. No definite cell pattern was identified with these neoplastic cells. A section from the gall bladder revealed a tumor arising from the lining epithelium and infiltrating through the muscularis. This tumor was infiltrating the adherent liver tissue directly and forming a mass of undifferentiated malignant cells. The focal area within the tumor mass showed the presence of PAS-positive, diastase-resistant, eosinophilic hyaline globules within the neoplastic cells. The immunohistochemistry test was diffusely positive for perinuclear anti-neutrophil cytoplasmic antibodies and negative for chromogranin, vimentin, Desmin, alpha-fetoprotein, leukocyte common antigen, CD34, and bcl2. When the clinical and radiological data are inconclusive, careful analysis of the histological and immunophenotypic features is needed to make the final diagnosis of UC of the gall bladder. The biological behavior and prognosis of this tumor remain unclear because of its rarity. Further studies will be needed to understand the characteristics of this deadly tumor and to establish an effective therapy for it.

We recently found that growth factor receptor-bound (Grb) protein 14 is a novel physiological modulator of photoreceptor specific cyclic nucleotide-gated channel alpha subunit (CNGA1). Grb14 promotes the CNG channel closure through its Ras-associating (RA) domain. In the current study we show that this RA domain-mediated inhibition of rod CNG channel is electrostatic in nature. Grb14 competes with cGMP for the CNGA1 binding pocket and electrostatically interacts with Arg(559) through a negatively charged β-turn at its RA domain. Moreover, the three Glu residues (180-182) in Grb14 are absolutely critical for electrostatic interaction with the cGMP binding pocket and resultant inhibition. Our study also demonstrates that substitution of Lys140 for Ala or in combination with polyglutamte mutants of Grb14 results in a significantly reduced binding with CNGA1. These results suggest that in addition to Glu(180-182) and Lys(140), other residues in Grb14 may be involved in the electrostatic interaction with CNGA1. The RA domain is highly conserved among the members of Grb7 family of proteins, which includes Grb7, Grb10 and Grb14. Further, only Grb14 is able to modulate the channel activity, but not Grb7 and Grb10. All together, it suggests the existence of a divergence in RA domains among the members of the Grb7 family.
Animals ; Calcium ; metabolism ; Cattle ; Cells, Cultured ; Cyclic GMP ; metabolism ; Cyclic Nucleotide-Gated Cation Channels ; chemistry ; genetics ; metabolism ; GRB10 Adaptor Protein ; genetics ; metabolism ; Humans ; Kidney ; cytology ; metabolism ; Models, Molecular ; Protein Conformation ; Protein-Tyrosine Kinases ; genetics ; metabolism ; Static Electricity

Ras proteins are signal-transducing GTPases that cycle between inactive GDP-bound and active GTP-bound forms. Ras is a prolific signaling molecule interacting with a spectrum of effector molecules and acting through more than one signaling pathway. The Ras-effector proteins contain a Ras-associating (RA) domain through which these associate with Ras in a GTP-dependent manner. The RA domain is highly conserved among the members of the growth factor receptor-bound (Grb) 7 family of proteins which includes Grb7, Grb10 and Grb14. Our laboratory has reported an unusual observation that RA domain of Grb14 binds to the C-terminal nucleotide binding site of cyclic nucleotide gated channel (CTRCNGA1) and inhibits the channel activity. Molecular modeling of the CTR-CNGA1 displays 50%-70% tertiary structural similarity towards Ras proteins. We named this region as Ras-like domain (RLD). The interaction between RA-Grb14 and RLD-CNGA1 is mediated through a simple protein-protein interaction temporally and spatially regulated by light and cGMP. It is interesting to note that Grb14 binds to GTPase-mutant Rab5, a Ras-related small GTPase whereas Grb10 binds only to GTP-bound form of active Rab5 but not to GTPase-defective mutant Rab5. These results suggest that Grb14 might have been evolved later in the evolution that binds to both Ras and nucleotide binding proteins such as CNGA1. Our studies also suggest that eukaryotic CNG channels could be evolved through a gene fusion between prokaryotic ion channels and cyclic nucleotide binding proteins, both of which might have undergone several sequence variations for functional adaptation during evolution.
Amino Acid Sequence ; Animals ; Cattle ; Cell Membrane ; metabolism ; radiation effects ; Conserved Sequence ; Cyclic Nucleotide-Gated Cation Channels ; genetics ; metabolism ; Evolution, Molecular ; Female ; GRB7 Adaptor Protein ; chemistry ; genetics ; metabolism ; HEK293 Cells ; Humans ; Light ; Male ; Models, Molecular ; Molecular Sequence Data ; Protein Binding ; radiation effects ; Protein Structure, Tertiary ; Protein Transport ; Rats ; Rod Cell Outer Segment ; radiation effects ; rab5 GTP-Binding Proteins ; metabolism ; ras Proteins ; metabolism