Increasing evidence indicates that proteins that associate with connexins may also regulate channel function. For example, the association of zonulae occludens-1 with both connexins and tight junction proteins suggests that crosstalk may exist between gap and tight junctions. Gap junctions are also modulated by the cystic fibrosis transmembrane conductance regulator, which may also be a part of the junctional complex, and by wnt-1, suggesting a link with b-catenin and cadherins in gap junctional regulation . However, the functional implications of these interactions are not well understood.
Connexin-specific gating mechanisms modify gap junctional communication. Acidic intracellular pH gates channels formed with Cx43 and Cx46, although not all connexins—for example, Cx37—are pH sensitive. Differential phosphorylation of connexins is another potential mechanism for gap junctional gating. Kinases implicated in this regulation include protein kinase C, which inhibits Cx43 assembly and thereby decreases Cx43-mediated gap junctional communication. A similar inhibitory effect on Cx43 gap junctions is attributed to MAP kinases and src kinases. These considerations indicate that connexin expression alone does not control the level of gap junctional communication; instead, crosstalk between connexins and other signaling pathways also needs to be considered.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.