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**13** 

 *Brazil*

**Gap Junction Intercellular Communication** 

**and Connexin Expression Profile in Normal** 

**Liver Cells and Hepatocarcinoma** 

*1Department of Cell and Developmental Biology, Institute of Biomedical* 

*2Institute of Biomedical Sciences, Federal University of Alfenas, Minas Gerais* 

Gap junction intercellular communication (GJIC) is considered to play a relevant role in homeostasis of multicellular organisms by regulating processes such as cell proliferation and cell differentiation. Specialized membrane structures mediate cell-to-cell communication, the gap junctional channels, which allow the transfer of molecules less than 1000Daltons (Da) between adjacent cells such as ions, aminoacids, nucleotides, metabolites and second messengers. Gap junctional channels consist of the two juxtaposed hemichannels called connexons, each of them constituted of six proteic subunits composed of connexin (Cx). These proteins are codified by multigene family with at least 21 members and their expression is tissue specific. The different isoforms are named according to their molecular mass (kilo Dalton) and they share a similar structure of four membrane-spanning domains, two extracellular loops, one cytoplasmic loop, one cytosolic N-terminal tail and Cterminal region. The transmembrane domains and the extracellular loops are highly conserved among the family members. N-terminus is also conserved, while the cytoplasmic loop and C-terminus show great variation in terms of sequence and length. Furthermore cytoplasmic tail and loop are susceptible to various post-translational modifications (including phosphorylation), which are important to modulate functional activity of

The liver represents an interesting system to study gap junction intercellular communication (GJIC) and through the years, a wealth of knowledge is available about functional GJIC and connexin expression profile in different physiological conditions which include cell proliferation, cell differentiation and cell death and disruption of GJIC has been associated

The synthesis, assembly and turnover of GJ channels follow the general secretory roles for membrane proteins. Connexins are synthesized by membrane-bound ribosomes and they are cotranslationally integrated into the endoplasmic reticulum membrane. The

**2. Gap junction channels biogenesis and degradation mechanisms** 

**1. Introduction** 

connexin (Figure 1).

with hepatocarcinogenesis process.

Glaucia M. Machado-Santelli1 and Marisa Ionta2

*Sciences,University of Sao Paulo, Sao Paulo* 

