4). to phosphorylation of different residues in the C-terminal area of Cx43. The use of antibodies specific for phosphorylation at defined residues offers allowed examination of specific phosphorylation events both in cells tradition and in vivo. These fresh antibody tools and those under development will allow us to correlate specific phosphorylation events with changes in connexin function. and Cx43 deficient mice pass away perinatally due to heart malformations [18]. Cx43() and Cx40(??) mice b-AP15 (NSC 687852) have heart conduction abnormalities [19, 20]. These disparate phenotypes not only show the diversity of the manifestation pattern of connexins, but they also illustrate that space junctions play different tasks in different cells. Mouse knock in experiments, in which one connexin isotype is definitely replaced with another, have shown that individual connexins play unique roles in specific cellular processes. For b-AP15 (NSC 687852) example, ablation of b-AP15 (NSC 687852) either the lens dietary fiber cell connexins Cx46 or Cx50 led to cataract formation while lens growth was only impaired in the Cx50-/-mice [21, 22]. Interestingly, targeted alternative of Cx50 with Cx46 corrected problems in differentiation and prevented cataract formation but did not restore growth control [23]. In additional mouse studies, when Cx43 was replaced by Cx32 or Cx40, the mice survived past birth but the developmental problems were only moderated by alternative with Cx32 and several additional problems became apparent in both groups of mice [24]. Alternative of Cx43 having a truncated version (Cx43K258Stop) lacking the C-terminal, cytoplasmic tail region yielded mice that died shortly after birth due to an epidermal barrier defect, not the heart defect that is present in Cx43 deficient mice [25]. The C-terminal region has been shown to have multiple sites of phosphorylation and protein interaction and hence is likely involved in Cx43 rules. Connexin phosphorylation has been examined several times recently [26-31]. Connexin phosphorylation has been correlated with changes in space junction assembly, stability and channel properties [26-31]. Connexins of the 3 major evolutionary organizations (, , and ) can be phosphorylated, and, given that cells can communicate multiple connexins, it seems likely that a solitary cell could communicate multiple phosphorylated connexins. However, no consensus connexin phosphorylation sequences between the different family members have been recognized. While most of the research has been performed in mammalian systems, both chick and fish connexins have been shown to be phosphorylated [32, 33]. Up until recently, essentially all of this study was based on cell tradition models. This review concentrates on the presence of Cx43 phosphorylation in cells and offers speculation within the role that these events play in cells function. These studies are possible because phosphorylation-state specific antibodies have become available for several phosphorylation sites b-AP15 (NSC 687852) in Cx43. 2. Phosphorylation of Cx43 Several reports have shown that Cx43 has a half-life in the range of 1-3 h in cultured cells or in cells [34-38]. A fast turnover rate could imply a high level of post-translational rules. Indeed, the pioneering work of Musil and Good enough, the Lau laboratory and several additional investigators have shown that Cx43 is definitely differentially phosphorylated throughout its existence cycle in homeostatic cells [34-36, 39-43]. Cx43 demonstrates multiple electrophoretic isoforms when analyzed by polyacrylamide gel electrophoresis (SDS-PAGE), including a faster migrating form that includes non-phosphorylated (P0 or NP) Cx43, and at least two slower migrating forms, generally termed P1 and P2. Both P1 Epha5 and P2 co-migrate with P0 following alkaline phosphatase treatment, suggesting that phosphorylation is the main covalent modification recognized in SDS-PAGE analysis [35, 42]. However, we while others have found that phosphorylated varieties can migrate with the P0 band in SDS-PAGE [44]. Phosphoamino acid.