Chemotaxis and its significance in biology and clinics Dr. habil. Kőhidai László 2019/02/20

Adhesion Chemotaxis Phagocytosis Other Cell-physiological effects (e.g. proliferation) Adhesion Chemotaxis Phagocytosis

Chemotaxis – Significance in biology Helps to distinguish / to approach food molecules Helps to avoid biologically harmful/toxic substances Sperm to approach oocyte - fertilization Tissue transformation processes (e.g. CNS) Immune reaction of multicellular organisms Proliferation and growing of tumors, formation of metastasis

Chemoattractant materials Chemorepellent materials

Basic concepts – Definitions 1 Chemotaxis: Migratory response of self-directed, motile cells. Direction and speed of migration is influenced by the concentration of molecules solved in the environment. VECTORIAL movement

Chemotaxis

Basic concepts – Definitions 2 Chemokinesis: Characteristic parameters (speed, frequency, amplitude) of motile cells are randomely changing due to the influence of environmental factors. NON vectorial !

Chemokinesis

Chemotaxis – Induced by dissolved molecules Concentration of meolacules inducing migration

Effect of molecules bound to the surface Haptotaxis Concentration gradient of molecules bound onto the surface

Necrotaxis LASER Migration of cells is modulated (induced or blocked) by the biologically active substances released from the dead cells.

Nekrotaxis

Conditions of migration Ligands/substances inducing the migration Motile cells Receptors capable to detect ligands Effector mechanisms – e.g. cytoskeletal system

Main steps accompanying receptor dependent migration of eukaryotes Deformation of the cell Cell adhesion Cilliary/ flagellar movement

Chemotactic substances

Main groups of chemoattractant ligands ions of inorganic salts (K+, Cl-) amino acids (methionine, serine) biogenic amines oligopeptides (bacterial tripeptides) hormones (insulin) chemokines (interleukin 8) feromones synthetic substances (drugs)

Target cells

„Classical” target cells bacteria „Classical” target cells amebas ciliated eukaryotes

Target cells in higher ranked organisms neutrophil granulocyte endothel monocyte lymphocyte eosinophil granulocyte

Receptors

Receptor classes Location Ligand Surface membrane Hormone Cytoplasme Nucleus Hormone Immune Nerve system Drug Ligand

Main characteristics of receptors Specificity – structure Affinity – effect at low conc. Saturabiliy – number of receptors Reversibility Specific response of the cell