Why to communicate/ cordinate1…….2…….3………….Communication levels

• Cellular level• Tissue• Organ level• Environment

Need for communication

TYPES OF COMMUNICATION

• Cell’s direct signaling or intracellular communication• Direct cell contacts

• Extra cellular communication or chemical signaling1. Paracrine 2. Autocrine signaling3. Endocrine signaling4. Synaptic signaling

vertebrates, 3 Types

1. Anchoring Junctions (connect the cytoskeletons of adjacent cells)a. Desmosomesb. Hemidesmosomesc. Adherens Junctions

2. Communicating (GAP) junctions (permit small molecules to pass between cells)

3. Tight Junctions (occluding junctions), create sheets of cells

CELL TO CELL CONTACTS/ JUNCTIONS

Junction Cytoskeletal Anchor

Transmembrane Linker Ties Cell To

Desmosomes Intermediate filaments Cadherin Other Cells

Hemidesmosomes Intermediate Filaments Integrins EC Matrix

Adherens junctions

Actin Filaments Cadherin/Integrins Other Cells / the

EC Matrix

Anchoring proteins extend through the plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighbouring cells as well as to proteins in the extracellular matrix .

VERTEBRATES

A: Anchoring Junctions

•Direct chemical communication between adjacent cellular cytoplasm through diffusion without contact of the extracellular fluid.•Six connexin proteins, interacting to form a cylinder with a pore in the centre.

2 adjacent cell connexons interact, they form the gap junction channel.

B: Communicating (GAP) junctions

VERTEBRATES

•Connexon pores vary in size n polarity and therefore can be specific depending on the connexin proteins that constitute each individual connexon•Heart muscle, brain, Retinal and skin cells

C: Tight junctions VERTEBRATES

tissue, organ or cell specific combination of proteins of the claudin, occluding, tricellulin and JAM families. Beside transmembrane proteins , a number of cytoplasmatic associated adaptor proteins are present, that mediate the regulation and connection of the tight junctions with the actic cytoskeleton

Branching network of sealing strands, each acting independently

• Efficiency of the junction in preventing ion passage increases exponentially with the number of strands.

• Regulate the movement of water and solutes between epithelial layers.

Tight epithelia like distal convoluted tubule, and the collecting duct part of the nephron in the kidney and the bile ducts ramifying through liver tissue.Leaky epithelia have less complex tight junctions. For instance, the tight junction in the kidney proximal tubule, a very leaky epithelium, has only two to three junctional strands, and these strands exhibit infrequent large slit breaks.

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Invertebrates: junctions, for example septate junctions or the C. elegans apical junction.

beneath the apical, lumenal surface of the intestinal cells

epithelial cells, barrier to solute diffusion through the intracellular space

CELL TO CELL CONTACTS/ JUNCTIONS

portions of the endoplasmic reticulum are trapped across the middle lamella in newly dividing plant cells eventually becoming (primary plasmodesmata). wall is not thickened further, and depressions or thin areas known as pits are formed

Alternatively, plasmodesmata can be inserted into existing cell walls between non-dividing cells (secondary plasmodesmata)

PLASMODESMATA

MULTICELLULAR PLANTS