You may already be familiar with what Hans Conzelmann reports in An Outline of the Theology of the New Testament (Grundriss der Theologie des Nuen Testaments), but I will cite a portion of that work that discusses Jude 4:
"Thus the Christian use of KURIOS cannot be derived from the LXX. The reverse is in fact the case. Once the title began to be used, it was found again in the Bible. KURIOS is, of course, a designation for God, not among the Greeks, but in Syria, Egypt and Asia Minor."
"On the one hand, Jesus exercises the functions of God as Lord: he rules over the world. On the other, however, he is clearly distinguished from God. The view is that God has delegated the rule of the world to Jesus for a particular time, from the exaltation to the parousia, and for a specific end, for the completion of the saving work, the subjection of the powers. Above all, 'Lord' designates Jesus as the permanent mediator of the relationship with God. So men call upon him" (page 87).
While noting that men and women call upon Jesus, Conzelmann makes it clear that the Bible does not refer to prayer when it speaks of humans calling upon Jesus:
"Calling on Jesus is to be distinguished from prayer. Only God is to be worshipped."